Auto merge of #21036 - emilio:gecko-sync, r=emilio

style: Sync changes from mozilla-central. See each individual commit for details.  --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21036)
2025-08-07 06:25:32 +01:00 · 2018-06-12 15:16:00 -04:00 · 2018-06-12 15:16:00 -04:00 · cad2b164dc
commit cad2b164dc
parent fc3c558cbf 2106cc46e5
43 changed files with 934 additions and 717 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -271,7 +271,7 @@ dependencies = [
 "azure 0.29.0 (git+https://github.com/servo/rust-azure)",
 "canvas_traits 0.0.1",
 "compositing 0.0.1",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "gleam 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@ -289,7 +289,7 @@ dependencies = [
 name = "canvas_traits"
 version = "0.0.1"
 dependencies = [
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "gleam 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "ipc-channel 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@ -563,30 +563,32 @@ dependencies = [
 [[package]]
 name = "cssparser"
-version = "0.23.2"
+version = "0.23.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cssparser-macros 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser-macros 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "dtoa-short 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "itoa 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itoa 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "proc-macro2 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "procedural-masquerade 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)",
 "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
 name = "cssparser-macros"
-version = "0.3.0"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "proc-macro2 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "procedural-masquerade 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
@ -1319,11 +1321,6 @@ dependencies = [
 "either 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
 name = "itoa"
 version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "itoa"
 version = "0.4.1"
@ -1615,7 +1612,7 @@ name = "malloc_size_of"
 version = "0.0.1"
 dependencies = [
 "app_units 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "hashglobe 0.1.0",
 "hyper 0.10.13 (registry+https://github.com/rust-lang/crates.io-index)",
@ -1625,7 +1622,7 @@ dependencies = [
 "serde 1.0.37 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde_bytes 0.10.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "servo_arc 0.1.1",
- "smallbitvec 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallbitvec 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "time 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2280,11 +2277,6 @@ name = "quick-error"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "quote"
 version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "quote"
 version = "0.5.1"
@ -2472,7 +2464,7 @@ dependencies = [
 "chrono 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "cmake 0.1.29 (registry+https://github.com/rust-lang/crates.io-index)",
 "cookie 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "deny_public_fields 0.0.1",
 "devtools_traits 0.0.1",
 "dom_struct 0.0.1",
@ -2549,7 +2541,7 @@ dependencies = [
 "app_units 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "atomic_refcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "canvas_traits 0.0.1",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "gfx_traits 0.0.1",
 "html5ever 0.22.3 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2631,7 +2623,7 @@ name = "selectors"
 version = "0.19.0"
 dependencies = [
 "bitflags 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2921,7 +2913,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "smallbitvec"
-version = "2.1.0"
+version = "2.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
@ -2981,7 +2973,7 @@ dependencies = [
 "bitflags 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "byteorder 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "encoding_rs 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "fallible 0.0.1",
@ -3012,7 +3004,7 @@ dependencies = [
 "servo_atoms 0.0.1",
 "servo_config 0.0.1",
 "servo_url 0.0.1",
- "smallbitvec 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallbitvec 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "style_derive 0.0.1",
@ -3042,7 +3034,7 @@ version = "0.0.1"
 dependencies = [
 "app_units 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "byteorder 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "html5ever 0.22.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "parking_lot 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
@ -3064,7 +3056,7 @@ version = "0.0.1"
 dependencies = [
 "app_units 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "bitflags 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "malloc_size_of 0.0.1",
 "malloc_size_of_derive 0.0.1",
@ -3081,16 +3073,6 @@ name = "swapper"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "syn"
 version = "0.11.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
 "synom 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "unicode-xid 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
 name = "syn"
 version = "0.13.1"
@ -3101,14 +3083,6 @@ dependencies = [
 "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
 name = "synom"
 version = "0.11.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "unicode-xid 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
 name = "synstructure"
 version = "0.8.1"
@ -3296,11 +3270,6 @@ name = "unicode-width"
 version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "unicode-xid"
 version = "0.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "unicode-xid"
 version = "0.1.0"
@ -3787,8 +3756,8 @@ dependencies = [
 "checksum crossbeam-deque 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f739f8c5363aca78cfb059edf753d8f0d36908c348f3d8d1503f03d8b75d9cf3"
 "checksum crossbeam-epoch 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "927121f5407de9956180ff5e936fe3cf4324279280001cd56b669d28ee7e9150"
 "checksum crossbeam-utils 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "2760899e32a1d58d5abb31129f8fae5de75220bc2176e77ff7c627ae45c918d9"
-"checksum cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)" = "8a807ac3ab7a217829c2a3b65732b926b2befe6a35f33b4bf8b503692430f223"
+"checksum cssparser 0.23.10 (registry+https://github.com/rust-lang/crates.io-index)" = "8f1c74d99b0f489cc546336b911452562ebfd4aec034b0c526cb77a3a02d3790"
-"checksum cssparser-macros 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "079adec4af52bb5275eadd004292028c79eb3c5f5b4ee8086a36d4197032f6df"
+"checksum cssparser-macros 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "f3a5383ae18dbfdeb569ed62019f5bddb2a95cd2d3833313c475a0d014777805"
 "checksum darling 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2a78af487e4eb8f4421a1770687b328af6bb4494ca93435210678c6eea875c11"
 "checksum darling_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b315f49c7b6db3708bca6e6913c194581a44ec619b7a39e131d4dd63733a3698"
 "checksum darling_macro 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "eb69a38fdeaeaf3db712e1df170de67ee9dfc24fb88ca3e9d21e703ec25a4d8e"
@ -3853,7 +3822,6 @@ dependencies = [
 "checksum iovec 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "dbe6e417e7d0975db6512b90796e8ce223145ac4e33c377e4a42882a0e88bb08"
 "checksum ipc-channel 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "db9daf099728ac5390c73f54e6e3708f0c514d2b51f24373830f568702eadfca"
 "checksum itertools 0.7.6 (registry+https://github.com/rust-lang/crates.io-index)" = "b07332223953b5051bceb67e8c4700aa65291535568e1f12408c43c4a42c0394"
 "checksum itoa 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8324a32baf01e2ae060e9de58ed0bc2320c9a2833491ee36cd3b4c414de4db8c"
 "checksum itoa 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c069bbec61e1ca5a596166e55dfe4773ff745c3d16b700013bcaff9a6df2c682"
 "checksum jemalloc-sys 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "479294d130502fada93c7a957e8d059b632b03d6204aca37af557dee947f30a9"
 "checksum jpeg-decoder 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)" = "0dfe27a6c0dabd772d0f9b9f8701c4ca12c4d1eebcadf2be1f6f70396f6a1434"
@ -3927,7 +3895,6 @@ dependencies = [
 "checksum proc-macro2 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "77997c53ae6edd6d187fec07ec41b207063b5ee6f33680e9fa86d405cdd313d4"
 "checksum procedural-masquerade 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c93cdc1fb30af9ddf3debc4afbdb0f35126cbd99daa229dd76cdd5349b41d989"
 "checksum quick-error 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "eda5fe9b71976e62bc81b781206aaa076401769b2143379d3eb2118388babac4"
 "checksum quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e920b65c65f10b2ae65c831a81a073a89edd28c7cce89475bff467ab4167a"
 "checksum quote 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7b0ff51282f28dc1b53fd154298feaa2e77c5ea0dba68e1fd8b03b72fbe13d2a"
 "checksum rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)" = "15a732abf9d20f0ad8eeb6f909bf6868722d9a06e1e50802b6a70351f40b4eb1"
 "checksum rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "eba5f8cb59cc50ed56be8880a5c7b496bfd9bd26394e176bc67884094145c2c5"
@ -3967,7 +3934,7 @@ dependencies = [
 "checksum signpost 0.1.0 (git+https://github.com/pcwalton/signpost.git)" = "<none>"
 "checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
 "checksum slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "17b4fcaed89ab08ef143da37bc52adbcc04d4a69014f4c1208d6b51f0c47bc23"
-"checksum smallbitvec 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "665fbc8384f961eb55c548daa2a4b1efff1f9d03b7a10f162ac6ad6a781ca966"
+"checksum smallbitvec 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5c63726029f0069f88467873e47f392575f28f9f16b72ac65465263db4b3a13c"
 "checksum smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "44db0ecb22921ef790d17ae13a3f6d15784183ff5f2a01aa32098c7498d2b4b9"
 "checksum stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "15132e0e364248108c5e2c02e3ab539be8d6f5d52a01ca9bbf27ed657316f02b"
 "checksum string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "25d70109977172b127fe834e5449e5ab1740b9ba49fa18a2020f509174f25423"
@ -3975,9 +3942,7 @@ dependencies = [
 "checksum string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b1884d1bc09741d466d9b14e6d37ac89d6909cbcac41dd9ae982d4d063bbedfc"
 "checksum strsim 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b4d15c810519a91cf877e7e36e63fe068815c678181439f2f29e2562147c3694"
 "checksum swapper 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e454d048db5527d000bfddb77bd072bbf3a1e2ae785f16d9bd116e07c2ab45eb"
 "checksum syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)" = "d3b891b9015c88c576343b9b3e41c2c11a51c219ef067b264bd9c8aa9b441dad"
 "checksum syn 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)" = "91b52877572087400e83d24b9178488541e3d535259e04ff17a63df1e5ceff59"
 "checksum synom 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a393066ed9010ebaed60b9eafa373d4b1baac186dd7e008555b0f702b51945b6"
 "checksum synstructure 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "98cad891cd238c98e1f0aec9f7c0f620aa696e4e5f7daba56ac67b5e86a6b049"
 "checksum tempfile 2.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "11ce2fe9db64b842314052e2421ac61a73ce41b898dc8e3750398b219c5fc1e0"
 "checksum tendril 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9de21546595a0873061940d994bbbc5c35f024ae4fd61ec5c5b159115684f508"
@ -4002,7 +3967,6 @@ dependencies = [
 "checksum unicode-script 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e8bd7bbf020b2885113e6304f68bcc33881c5552657c58d4e9699cd1b6606e81"
 "checksum unicode-segmentation 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a8083c594e02b8ae1654ae26f0ade5158b119bd88ad0e8227a5d8fcd72407946"
 "checksum unicode-width 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "bf3a113775714a22dcb774d8ea3655c53a32debae63a063acc00a91cc586245f"
 "checksum unicode-xid 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8c1f860d7d29cf02cb2f3f359fd35991af3d30bac52c57d265a3c461074cb4dc"
 "checksum unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
 "checksum unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "382810877fe448991dfc7f0dd6e3ae5d58088fd0ea5e35189655f84e6814fa56"
 "checksum url 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fa35e768d4daf1d85733418a49fb42e10d7f633e394fccab4ab7aba897053fe2"
--- a/components/script/dom/cssstyledeclaration.rs
+++ b/components/script/dom/cssstyledeclaration.rs
@ -253,7 +253,7 @@ impl CSSStyleDeclaration {
        self.owner.mutate_associated_block(|pdb, changed| {
            if value.is_empty() {
                // Step 3
-                *changed = pdb.remove_property(&id);
+                *changed = pdb.remove_property(&id, |_| {});
                return Ok(());
            }
@ -365,7 +365,7 @@ impl CSSStyleDeclarationMethods for CSSStyleDeclaration {
        let mut string = String::new();
        self.owner.mutate_associated_block(|pdb, changed| {
            pdb.property_value_to_css(&id, &mut string).unwrap();
-            *changed = pdb.remove_property(&id);
+            *changed = pdb.remove_property(&id, |_| {});
        });
        // Step 6
--- a/components/selectors/builder.rs
+++ b/components/selectors/builder.rs
@ -36,6 +36,7 @@ use std::slice;
 /// (from left to right). Once the process is complete, callers should invoke
 /// build(), which transforms the contents of the SelectorBuilder into a heap-
 /// allocated Selector and leaves the builder in a drained state.
 #[derive(Debug)]
 pub struct SelectorBuilder<Impl: SelectorImpl> {
    /// The entire sequence of simple selectors, from left to right, without combinators.
    ///
@ -104,7 +105,7 @@ impl<Impl: SelectorImpl> SelectorBuilder<Impl> {
        parsed_slotted: bool,
    ) -> ThinArc<SpecificityAndFlags, Component<Impl>> {
        // Compute the specificity and flags.
-        let mut spec = SpecificityAndFlags(specificity(self.simple_selectors.iter()));
+        let mut spec = SpecificityAndFlags(specificity(&*self, self.simple_selectors.iter()));
        if parsed_pseudo {
            spec.0 |= HAS_PSEUDO_BIT;
        }
@ -268,25 +269,35 @@ impl From<Specificity> for u32 {
    }
 }
-fn specificity<Impl>(iter: slice::Iter<Component<Impl>>) -> u32
+fn specificity<Impl>(builder: &SelectorBuilder<Impl>, iter: slice::Iter<Component<Impl>>) -> u32
 where
    Impl: SelectorImpl,
 {
-    complex_selector_specificity(iter).into()
+    complex_selector_specificity(builder, iter).into()
 }
-fn complex_selector_specificity<Impl>(mut iter: slice::Iter<Component<Impl>>) -> Specificity
+fn complex_selector_specificity<Impl>(
    builder: &SelectorBuilder<Impl>,
    mut iter: slice::Iter<Component<Impl>>,
 ) -> Specificity
 where
    Impl: SelectorImpl,
 {
    fn simple_selector_specificity<Impl>(
        builder: &SelectorBuilder<Impl>,
        simple_selector: &Component<Impl>,
        specificity: &mut Specificity,
    ) where
        Impl: SelectorImpl,
    {
        match *simple_selector {
-            Component::Combinator(..) => unreachable!(),
+            Component::Combinator(ref combinator) => {
                unreachable!(
                    "Found combinator {:?} in simple selectors vector? {:?}",
                    combinator,
                    builder,
                );
            }
            // FIXME(emilio): Spec doesn't define any particular specificity for
            // ::slotted(), so apply the general rule for pseudos per:
            //
@ -326,7 +337,7 @@ where
            },
            Component::Negation(ref negated) => {
                for ss in negated.iter() {
-                    simple_selector_specificity(&ss, specificity);
+                    simple_selector_specificity(builder, &ss, specificity);
                }
            },
        }
@ -334,7 +345,7 @@ where
    let mut specificity = Default::default();
    for simple_selector in &mut iter {
-        simple_selector_specificity(&simple_selector, &mut specificity);
+        simple_selector_specificity(builder, &simple_selector, &mut specificity);
    }
    specificity
 }
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@ -92,7 +92,7 @@ macro_rules! with_all_bounds {
        /// NB: We need Clone so that we can derive(Clone) on struct with that
        /// are parameterized on SelectorImpl. See
        /// <https://github.com/rust-lang/rust/issues/26925>
-        pub trait SelectorImpl: Clone + Sized + 'static {
+        pub trait SelectorImpl: Clone + Debug + Sized + 'static {
            type ExtraMatchingData: Sized + Default + 'static;
            type AttrValue: $($InSelector)*;
            type Identifier: $($InSelector)*;
@ -544,10 +544,26 @@ impl<Impl: SelectorImpl> Selector<Impl> {
    }
    /// Whether this selector is a featureless :host selector, with no
-    /// combinators to the left.
+    /// combinators to the left, and optionally has a pseudo-element to the
    /// right.
    #[inline]
-    pub fn is_featureless_host_selector(&self) -> bool {
+    pub fn is_featureless_host_selector_or_pseudo_element(&self) -> bool {
-        self.iter().is_featureless_host_selector()
+        let mut iter = self.iter();
        if !self.has_pseudo_element() {
            return iter.is_featureless_host_selector();
        }
        // Skip the pseudo-element.
        for _ in &mut iter { }
        match iter.next_sequence() {
            None => return false,
            Some(combinator) => {
                debug_assert_eq!(combinator, Combinator::PseudoElement);
            }
        }
        iter.is_featureless_host_selector()
    }
    /// Returns an iterator over this selector in matching order (right-to-left),
--- a/components/style/Cargo.toml
+++ b/components/style/Cargo.toml
@ -59,7 +59,7 @@ serde = {version = "1.0", optional = true, features = ["derive"]}
 servo_arc = { path = "../servo_arc" }
 servo_atoms = {path = "../atoms", optional = true}
 servo_config = {path = "../config", optional = true}
-smallbitvec = "2.1.0"
+smallbitvec = "2.1.1"
 smallvec = "0.6"
 string_cache = { version = "0.7", optional = true }
 style_derive = {path = "../style_derive"}
--- a/components/style/animation.rs
+++ b/components/style/animation.rs
@ -10,7 +10,7 @@ use context::SharedStyleContext;
 use dom::{OpaqueNode, TElement};
 use font_metrics::FontMetricsProvider;
 use properties::{self, CascadeFlags, ComputedValues, LonghandId};
-use properties::animated_properties::{AnimatedProperty, TransitionProperty};
+use properties::animated_properties::AnimatedProperty;
 use properties::longhands::animation_direction::computed_value::single_value::T as AnimationDirection;
 use properties::longhands::animation_play_state::computed_value::single_value::T as AnimationPlayState;
 use rule_tree::CascadeLevel;
@ -20,6 +20,7 @@ use std::sync::mpsc::Sender;
 use stylesheets::keyframes_rule::{KeyframesAnimation, KeyframesStep, KeyframesStepValue};
 use timer::Timer;
 use values::computed::Time;
 use values::computed::box_::TransitionProperty;
 use values::computed::transform::TimingFunction;
 use values::generics::box_::AnimationIterationCount;
 use values::generics::transform::{StepPosition, TimingFunction as GenericTimingFunction};
@ -303,7 +304,8 @@ impl PropertyAnimation {
        let duration = box_style.transition_duration_mod(transition_index);
        match transition_property {
-            TransitionProperty::Unsupported(_) => result,
+            TransitionProperty::Custom(..) |
            TransitionProperty::Unsupported(..) => result,
            TransitionProperty::Shorthand(ref shorthand_id) => shorthand_id
                .longhands()
                .filter_map(|longhand| {
--- a/components/style/font_face.rs
+++ b/components/style/font_face.rs
@ -323,7 +323,7 @@ macro_rules! is_descriptor_enabled {
    ("font-variation-settings") => {
        unsafe {
            use gecko_bindings::structs::mozilla;
-            mozilla::StaticPrefs_sVarCache_layout_css_font_variations_enabled
+            mozilla::StaticPrefs_sVarCache_layout_css_font_variations_enabled != 0
        }
    };
    ($name:tt) => {
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@ -67,7 +67,6 @@ use media_queries::Device;
 use properties::{ComputedValues, LonghandId};
 use properties::{Importance, PropertyDeclaration, PropertyDeclarationBlock};
 use properties::animated_properties::{AnimationValue, AnimationValueMap};
 use properties::animated_properties::TransitionProperty;
 use properties::style_structs::Font;
 use rule_tree::CascadeLevel as ServoCascadeLevel;
 use selector_parser::{AttrValue, Direction, PseudoClassStringArg};
@ -181,7 +180,6 @@ impl<'lr> TShadowRoot for GeckoShadowRoot<'lr> {
        let author_styles = AuthorStyles::<GeckoStyleSheet>::from_ffi(author_styles);
        debug_assert!(!author_styles.stylesheets.dirty());
        debug_assert!(
            author_styles.quirks_mode == self.as_node().owner_doc().quirks_mode() ||
                author_styles.stylesheets.is_empty()
@ -617,31 +615,37 @@ impl<'le> GeckoElement<'le> {
    // GeckoNode is a raw reference.
    //
    // We can use a Cell<T>, but that's a bit of a pain.
    #[inline]
    fn set_flags(&self, flags: u32) {
        unsafe { Gecko_SetNodeFlags(self.as_node().0, flags) }
    }
    #[inline]
    unsafe fn unset_flags(&self, flags: u32) {
        Gecko_UnsetNodeFlags(self.as_node().0, flags)
    }
    /// Returns true if this element has descendants for lazy frame construction.
    #[inline]
    pub fn descendants_need_frames(&self) -> bool {
        self.flags() & (NODE_DESCENDANTS_NEED_FRAMES as u32) != 0
    }
    /// Returns true if this element needs lazy frame construction.
    #[inline]
    pub fn needs_frame(&self) -> bool {
        self.flags() & (NODE_NEEDS_FRAME as u32) != 0
    }
    /// Returns a reference to the DOM slots for this Element, if they exist.
    #[inline]
    fn dom_slots(&self) -> Option<&structs::FragmentOrElement_nsDOMSlots> {
        let slots = self.as_node().0.mSlots as *const structs::FragmentOrElement_nsDOMSlots;
        unsafe { slots.as_ref() }
    }
    /// Returns a reference to the extended DOM slots for this Element.
    #[inline]
    fn extended_slots(&self) -> Option<&structs::FragmentOrElement_nsExtendedDOMSlots> {
        self.dom_slots().and_then(|s| unsafe {
            (s._base.mExtendedSlots.mPtr as *const structs::FragmentOrElement_nsExtendedDOMSlots)
@ -699,6 +703,7 @@ impl<'le> GeckoElement<'le> {
        }
    }
    #[inline]
    fn non_xul_xbl_binding_parent_raw_content(&self) -> *mut nsIContent {
        debug_assert!(!self.is_xul_element());
        self.extended_slots()
@ -1113,7 +1118,23 @@ impl<'le> TElement for GeckoElement<'le> {
            assert_eq!(base as *const _, self.0 as *const _, "Bad cast");
        }
-        let assigned_nodes: &[structs::RefPtr<structs::nsINode>] = &*slot.mAssignedNodes;
+        // FIXME(emilio): Workaround a bindgen bug on Android that causes
        // mAssignedNodes to be at the wrong offset. See bug 1466406.
        //
        // Bug 1466580 tracks running the Android layout tests on automation.
        //
        // The actual bindgen bug still needs reduction.
        let assigned_nodes: &[structs::RefPtr<structs::nsINode>] =
            if !cfg!(target_os = "android") {
                debug_assert_eq!(
                    unsafe { bindings::Gecko_GetAssignedNodes(self.0) },
                    &slot.mAssignedNodes as *const _,
                );
                &*slot.mAssignedNodes
            } else {
                unsafe { &**bindings::Gecko_GetAssignedNodes(self.0) }
            };
        debug_assert_eq!(
            mem::size_of::<structs::RefPtr<structs::nsINode>>(),
@ -1351,6 +1372,7 @@ impl<'le> TElement for GeckoElement<'le> {
        !self.is_in_native_anonymous_subtree()
    }
    #[inline]
    fn implemented_pseudo_element(&self) -> Option<PseudoElement> {
        if !self.is_in_native_anonymous_subtree() {
            return None;
@ -1364,6 +1386,7 @@ impl<'le> TElement for GeckoElement<'le> {
        PseudoElement::from_pseudo_type(pseudo_type)
    }
    #[inline]
    fn store_children_to_process(&self, _: isize) {
        // This is only used for bottom-up traversal, and is thus a no-op for Gecko.
    }
@ -1587,6 +1610,7 @@ impl<'le> TElement for GeckoElement<'le> {
    ) -> bool {
        use gecko_bindings::structs::nsCSSPropertyID;
        use properties::LonghandIdSet;
        use values::computed::TransitionProperty;
        debug_assert!(
            self.might_need_transitions_update(Some(before_change_style), after_change_style),
@ -1630,6 +1654,7 @@ impl<'le> TElement for GeckoElement<'le> {
            };
            match transition_property {
                TransitionProperty::Custom(..) |
                TransitionProperty::Unsupported(..) => {},
                TransitionProperty::Shorthand(ref shorthand) => {
                    if shorthand.longhands().any(property_check_helper) {
--- a/components/style/gecko_bindings/sugar/ns_compatibility.rs
+++ b/components/style/gecko_bindings/sugar/ns_compatibility.rs
@ -8,6 +8,7 @@ use context::QuirksMode;
 use gecko_bindings::structs::nsCompatibility;
 impl From<nsCompatibility> for QuirksMode {
    #[inline]
    fn from(mode: nsCompatibility) -> QuirksMode {
        match mode {
            nsCompatibility::eCompatibility_FullStandards => QuirksMode::NoQuirks,
--- a/components/style/gecko_bindings/sugar/refptr.rs
+++ b/components/style/gecko_bindings/sugar/refptr.rs
@ -4,7 +4,8 @@
 //! A rust helper to ease the use of Gecko's refcounted types.
-use gecko_bindings::structs;
+use Atom;
 use gecko_bindings::{structs, bindings};
 use gecko_bindings::sugar::ownership::HasArcFFI;
 use servo_arc::Arc;
 use std::{fmt, mem, ptr};
@ -255,13 +256,16 @@ unsafe impl<T: ThreadSafeRefCounted> Send for RefPtr<T> {}
 unsafe impl<T: ThreadSafeRefCounted> Sync for RefPtr<T> {}
 macro_rules! impl_refcount {
-    ($t:ty, $addref:ident, $release:ident) => {
+    ($t:ty, $addref:path, $release:path) => {
        unsafe impl RefCounted for $t {
            #[inline]
            fn addref(&self) {
-                unsafe { ::gecko_bindings::bindings::$addref(self as *const _ as *mut _) }
+                unsafe { $addref(self as *const _ as *mut _) }
            }
            #[inline]
            unsafe fn release(&self) {
-                ::gecko_bindings::bindings::$release(self as *const _ as *mut _)
+                $release(self as *const _ as *mut _)
            }
        }
    };
@ -271,50 +275,63 @@ macro_rules! impl_refcount {
 //
 // Gets you a free RefCounted impl implemented via FFI.
 macro_rules! impl_threadsafe_refcount {
-    ($t:ty, $addref:ident, $release:ident) => {
+    ($t:ty, $addref:path, $release:path) => {
        impl_refcount!($t, $addref, $release);
        unsafe impl ThreadSafeRefCounted for $t {}
    };
 }
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::RawGeckoURLExtraData,
+    structs::RawGeckoURLExtraData,
-    Gecko_AddRefURLExtraDataArbitraryThread,
+    bindings::Gecko_AddRefURLExtraDataArbitraryThread,
-    Gecko_ReleaseURLExtraDataArbitraryThread
+    bindings::Gecko_ReleaseURLExtraDataArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::nsStyleQuoteValues,
+    structs::nsStyleQuoteValues,
-    Gecko_AddRefQuoteValuesArbitraryThread,
+    bindings::Gecko_AddRefQuoteValuesArbitraryThread,
-    Gecko_ReleaseQuoteValuesArbitraryThread
+    bindings::Gecko_ReleaseQuoteValuesArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::nsCSSValueSharedList,
+    structs::nsCSSValueSharedList,
-    Gecko_AddRefCSSValueSharedListArbitraryThread,
+    bindings::Gecko_AddRefCSSValueSharedListArbitraryThread,
-    Gecko_ReleaseCSSValueSharedListArbitraryThread
+    bindings::Gecko_ReleaseCSSValueSharedListArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::mozilla::css::URLValue,
+    structs::mozilla::css::URLValue,
-    Gecko_AddRefCSSURLValueArbitraryThread,
+    bindings::Gecko_AddRefCSSURLValueArbitraryThread,
-    Gecko_ReleaseCSSURLValueArbitraryThread
+    bindings::Gecko_ReleaseCSSURLValueArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::mozilla::css::GridTemplateAreasValue,
+    structs::mozilla::css::GridTemplateAreasValue,
-    Gecko_AddRefGridTemplateAreasValueArbitraryThread,
+    bindings::Gecko_AddRefGridTemplateAreasValueArbitraryThread,
-    Gecko_ReleaseGridTemplateAreasValueArbitraryThread
+    bindings::Gecko_ReleaseGridTemplateAreasValueArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::ImageValue,
+    structs::ImageValue,
-    Gecko_AddRefImageValueArbitraryThread,
+    bindings::Gecko_AddRefImageValueArbitraryThread,
-    Gecko_ReleaseImageValueArbitraryThread
+    bindings::Gecko_ReleaseImageValueArbitraryThread
 );
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::SharedFontList,
+    structs::SharedFontList,
-    Gecko_AddRefSharedFontListArbitraryThread,
+    bindings::Gecko_AddRefSharedFontListArbitraryThread,
-    Gecko_ReleaseSharedFontListArbitraryThread
+    bindings::Gecko_ReleaseSharedFontListArbitraryThread
 );
 impl_threadsafe_refcount!(
    structs::SheetLoadDataHolder,
    bindings::Gecko_AddRefSheetLoadDataHolderArbitraryThread,
    bindings::Gecko_ReleaseSheetLoadDataHolderArbitraryThread
 );
 #[inline]
 unsafe fn addref_atom(atom: *mut structs::nsAtom) {
    mem::forget(Atom::from_raw(atom));
 }
 #[inline]
 unsafe fn release_atom(atom: *mut structs::nsAtom) {
    let _ = Atom::from_addrefed(atom);
 }
 impl_threadsafe_refcount!(
-    ::gecko_bindings::structs::SheetLoadDataHolder,
+    structs::nsAtom,
-    Gecko_AddRefSheetLoadDataHolderArbitraryThread,
+    addref_atom,
-    Gecko_ReleaseSheetLoadDataHolderArbitraryThread
+    release_atom
 );
--- a/components/style/gecko_bindings/sugar/style_complex_color.rs
+++ b/components/style/gecko_bindings/sugar/style_complex_color.rs
@ -5,28 +5,21 @@
 //! Rust helpers to interact with Gecko's StyleComplexColor.
 use gecko::values::{convert_nscolor_to_rgba, convert_rgba_to_nscolor};
-use gecko_bindings::structs::{nscolor, StyleComplexColor};
+use gecko_bindings::structs::StyleComplexColor;
 use gecko_bindings::structs::StyleComplexColor_Tag as Tag;
 use values::{Auto, Either};
-use values::computed::Color as ComputedColor;
+use values::computed::{Color as ComputedColor, RGBAColor as ComputedRGBA};
 use values::computed::ui::ColorOrAuto;
-
+use values::generics::color::{Color as GenericColor, ComplexColorRatios};
 impl From<nscolor> for StyleComplexColor {
    fn from(other: nscolor) -> Self {
        StyleComplexColor {
            mColor: other,
            mForegroundRatio: 0,
            mIsAuto: false,
        }
    }
 }
 impl StyleComplexColor {
    /// Create a `StyleComplexColor` value that represents `currentColor`.
    pub fn current_color() -> Self {
        StyleComplexColor {
            mColor: 0,
-            mForegroundRatio: 255,
+            mBgRatio: 0.,
-            mIsAuto: false,
+            mFgRatio: 1.,
            mTag: Tag::eForeground,
        }
    }
@ -34,28 +27,66 @@ impl StyleComplexColor {
    pub fn auto() -> Self {
        StyleComplexColor {
            mColor: 0,
-            mForegroundRatio: 255,
+            mBgRatio: 0.,
-            mIsAuto: true,
+            mFgRatio: 1.,
            mTag: Tag::eAuto,
        }
    }
 }
 impl From<ComputedRGBA> for StyleComplexColor {
    fn from(other: ComputedRGBA) -> Self {
        StyleComplexColor {
            mColor: convert_rgba_to_nscolor(&other),
            mBgRatio: 1.,
            mFgRatio: 0.,
            mTag: Tag::eNumeric,
        }
    }
 }
 impl From<ComputedColor> for StyleComplexColor {
    fn from(other: ComputedColor) -> Self {
-        StyleComplexColor {
+        match other {
-            mColor: convert_rgba_to_nscolor(&other.color).into(),
+            GenericColor::Numeric(color) => color.into(),
-            mForegroundRatio: other.foreground_ratio,
+            GenericColor::Foreground => Self::current_color(),
-            mIsAuto: false,
+            GenericColor::Complex(color, ratios) => {
                debug_assert!(ratios != ComplexColorRatios::NUMERIC);
                debug_assert!(ratios != ComplexColorRatios::FOREGROUND);
                StyleComplexColor {
                    mColor: convert_rgba_to_nscolor(&color).into(),
                    mBgRatio: ratios.bg,
                    mFgRatio: ratios.fg,
                    mTag: Tag::eComplex,
                }
            }
        }
    }
 }
 impl From<StyleComplexColor> for ComputedColor {
    fn from(other: StyleComplexColor) -> Self {
-        debug_assert!(!other.mIsAuto);
+        match other.mTag {
-        ComputedColor {
+            Tag::eNumeric => {
-            color: convert_nscolor_to_rgba(other.mColor),
+                debug_assert!(other.mBgRatio == 1. && other.mFgRatio == 0.);
-            foreground_ratio: other.mForegroundRatio,
+                GenericColor::Numeric(convert_nscolor_to_rgba(other.mColor))
            }
            Tag::eForeground => {
                debug_assert!(other.mBgRatio == 0. && other.mFgRatio == 1.);
                GenericColor::Foreground
            }
            Tag::eComplex => {
                debug_assert!(other.mBgRatio != 1. || other.mFgRatio != 0.);
                debug_assert!(other.mBgRatio != 0. || other.mFgRatio != 1.);
                GenericColor::Complex(
                    convert_nscolor_to_rgba(other.mColor),
                    ComplexColorRatios {
                        bg: other.mBgRatio,
                        fg: other.mFgRatio,
                    },
                )
            }
            Tag::eAuto => unreachable!("Unsupport StyleComplexColor with tag eAuto"),
        }
    }
 }
@ -71,7 +102,7 @@ impl From<ColorOrAuto> for StyleComplexColor {
 impl From<StyleComplexColor> for ColorOrAuto {
    fn from(other: StyleComplexColor) -> Self {
-        if !other.mIsAuto {
+        if other.mTag != Tag::eAuto {
            Either::First(other.into())
        } else {
            Either::Second(Auto)
--- a/components/style/parser.rs
+++ b/components/style/parser.rs
@ -150,10 +150,19 @@ impl<'a> ParserContext<'a> {
    }
 }
 // XXXManishearth Replace all specified value parse impls with impls of this
 // trait. This will make it easy to write more generic values in the future.
 /// A trait to abstract parsing of a specified value given a `ParserContext` and
 /// CSS input.
 ///
 /// This can be derived on keywords with `#[derive(Parse)]`.
 ///
 /// The derive code understands the following attributes on each of the variants:
 ///
 ///  * `#[parse(aliases = "foo,bar")]` can be used to alias a value with another
 ///    at parse-time.
 ///
 ///  * `#[parse(condition = "function")]` can be used to make the parsing of the
 ///    value conditional on `function`, which needs to fulfill
 ///    `fn(&ParserContext) -> bool`.
 pub trait Parse: Sized {
    /// Parse a value of this type.
    ///
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@ -226,6 +226,10 @@ class Longhand(object):
        # See compute_damage for the various values this can take
        self.servo_restyle_damage = servo_restyle_damage
    @staticmethod
    def type():
        return "longhand"
    def experimental(self, product):
        if product == "gecko":
            return bool(self.gecko_pref)
@ -361,6 +365,10 @@ class Shorthand(object):
    animatable = property(get_animatable)
    transitionable = property(get_transitionable)
    @staticmethod
    def type():
        return "shorthand"
    def experimental(self, product):
        if product == "gecko":
            return bool(self.gecko_pref)
@ -392,6 +400,10 @@ class Alias(object):
        self.allowed_in_page_rule = original.allowed_in_page_rule
        self.allowed_in_keyframe_block = original.allowed_in_keyframe_block
    @staticmethod
    def type():
        return "alias"
    def experimental(self, product):
        if product == "gecko":
            return bool(self.gecko_pref)
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@ -492,9 +492,9 @@ impl PropertyDeclarationBlock {
    ///     declaration with more importance, and will ensure that, if inserted,
    ///     it's inserted at the end of the declaration block.
    ///
-    ///   * For `DeclarationSource::CssOm`, this will override importance and
+    ///   * For `DeclarationSource::CssOm`, this will override importance.
    ///     will preserve the original position on the block.
    ///
    /// Returns whether the declaration has changed.
    pub fn push(
        &mut self,
        declaration: PropertyDeclaration,
@ -517,15 +517,15 @@ impl PropertyDeclarationBlock {
                    continue;
                }
                let important = self.declarations_importance[i];
                // For declarations from parsing, non-important declarations
                // shouldn't override existing important one.
                if important && !importance.important() &&
                    matches!(source, DeclarationSource::Parsing) {
                    return true;
                }
                if matches!(source, DeclarationSource::Parsing) {
                    let important = self.declarations_importance[i];
                    // For declarations from parsing, non-important declarations
                    // shouldn't override existing important one.
                    if important && !importance.important() {
                        return false;
                    }
                    // As a compatibility hack, specially on Android,
                    // don't allow to override a prefixed webkit display
                    // value with an unprefixed version from parsing
@ -564,27 +564,17 @@ impl PropertyDeclarationBlock {
        true
    }
    /// Set the declaration importance for a given property, if found.
    ///
    /// Returns whether any declaration was updated.
    pub fn set_importance(&mut self, property: &PropertyId, new_importance: Importance) -> bool {
        let mut updated_at_least_one = false;
        for (i, declaration) in self.declarations.iter().enumerate() {
            if declaration.id().is_or_is_longhand_of(property) {
                let is_important = new_importance.important();
                if self.declarations_importance[i] != is_important {
                    self.declarations_importance.set(i, is_important);
                    updated_at_least_one = true;
                }
            }
        }
        updated_at_least_one
    }
    /// <https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-removeproperty>
    ///
    /// Returns whether any declaration was actually removed.
-    pub fn remove_property(&mut self, property: &PropertyId) -> bool {
+    pub fn remove_property<C>(
        &mut self,
        property: &PropertyId,
        mut before_change_callback: C,
    ) -> bool
    where
        C: FnMut(&Self),
    {
        let longhand_id = property.longhand_id();
        if let Some(id) = longhand_id {
            if !self.longhands.contains(id) {
@ -592,23 +582,28 @@ impl PropertyDeclarationBlock {
            }
        }
        let mut removed_at_least_one = false;
        let longhands = &mut self.longhands;
        let declarations_importance = &mut self.declarations_importance;
        let mut i = 0;
-        self.declarations.retain(|declaration| {
+        let mut len = self.len();
-            let id = declaration.id();
+        while i < len {
-            let remove = id.is_or_is_longhand_of(property);
+            {
-            if remove {
+                let id = self.declarations[i].id();
                if !id.is_or_is_longhand_of(property) {
                    i += 1;
                    continue;
                }
                if !removed_at_least_one {
                    before_change_callback(&*self);
                }
                removed_at_least_one = true;
                if let PropertyDeclarationId::Longhand(id) = id {
-                    longhands.remove(id);
+                    self.longhands.remove(id);
                }
-                declarations_importance.remove(i);
+                self.declarations_importance.remove(i);
            } else {
                i += 1;
            }
-            !remove
+            self.declarations.remove(i);
-        });
+            len -= 1;
        }
        if longhand_id.is_some() {
            debug_assert!(removed_at_least_one);
@ -1116,9 +1111,7 @@ where
    let mut parser = Parser::new(&mut input);
    let start_position = parser.position();
    parser.parse_entirely(|parser| {
-        let name = id.name().into();
+        PropertyDeclaration::parse_into(declarations, id, &context, parser)
        PropertyDeclaration::parse_into(declarations, id, name, &context, parser)
            .map_err(|e| e.into())
    }).map_err(|err| {
        let location = err.location;
        let error = ContextualParseError::UnsupportedPropertyDeclaration(
@ -1169,7 +1162,7 @@ impl<'a, 'b, 'i> DeclarationParser<'i> for PropertyDeclarationParser<'a, 'b> {
            }
        };
        input.parse_until_before(Delimiter::Bang, |input| {
-            PropertyDeclaration::parse_into(self.declarations, id, name, self.context, input)
+            PropertyDeclaration::parse_into(self.declarations, id, self.context, input)
        })?;
        let importance = match input.try(parse_important) {
            Ok(()) => Importance::Important,
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@ -28,7 +28,6 @@ use gecko_bindings::bindings::Gecko_CopyListStyleImageFrom;
 use gecko_bindings::bindings::Gecko_EnsureImageLayersLength;
 use gecko_bindings::bindings::Gecko_SetCursorArrayLength;
 use gecko_bindings::bindings::Gecko_SetCursorImageValue;
 use gecko_bindings::bindings::Gecko_StyleTransition_SetUnsupportedProperty;
 use gecko_bindings::bindings::Gecko_NewCSSShadowArray;
 use gecko_bindings::bindings::Gecko_nsStyleFont_SetLang;
 use gecko_bindings::bindings::Gecko_nsStyleFont_CopyLangFrom;
@ -49,7 +48,6 @@ use gecko::values::GeckoStyleCoordConvertible;
 use gecko::values::round_border_to_device_pixels;
 use logical_geometry::WritingMode;
 use media_queries::Device;
 use properties::animated_properties::TransitionProperty;
 use properties::computed_value_flags::*;
 use properties::{longhands, Importance, LonghandId};
 use properties::{PropertyDeclaration, PropertyDeclarationBlock, PropertyDeclarationId};
@ -60,7 +58,7 @@ use std::marker::PhantomData;
 use std::mem::{forget, uninitialized, transmute, zeroed};
 use std::{cmp, ops, ptr};
 use values::{self, CustomIdent, Either, KeyframesName, None_};
-use values::computed::{NonNegativeLength, ToComputedValue, Percentage};
+use values::computed::{NonNegativeLength, ToComputedValue, Percentage, TransitionProperty};
 use values::computed::font::FontSize;
 use values::computed::effects::{BoxShadow, Filter, SimpleShadow};
 use values::computed::outline::OutlineStyle;
@ -390,17 +388,9 @@ impl ${style_struct.gecko_struct_name} {
 <%!
 def get_gecko_property(ffi_name, self_param = "self"):
    if "mBorderColor" in ffi_name:
        return ffi_name.replace("mBorderColor",
                                "unsafe { *%s.gecko.__bindgen_anon_1.mBorderColor.as_ref() }"
                                % self_param)
    return "%s.gecko.%s" % (self_param, ffi_name)
 def set_gecko_property(ffi_name, expr):
    if "mBorderColor" in ffi_name:
        ffi_name = ffi_name.replace("mBorderColor",
                                    "*self.gecko.__bindgen_anon_1.mBorderColor.as_mut()")
        return "unsafe { %s = %s };" % (ffi_name, expr)
    return "self.gecko.%s = %s;" % (ffi_name, expr)
 %>
@ -1596,7 +1586,7 @@ fn static_assert() {
        self.gecko.mComputedBorder.${side.ident} = self.gecko.mBorder.${side.ident};
    }
-    <% impl_color("border_%s_color" % side.ident, "(mBorderColor)[%s]" % side.index) %>
+    <% impl_color("border_%s_color" % side.ident, "mBorder%sColor" % side.name) %>
    <% impl_non_negative_length("border_%s_width" % side.ident,
                                "mComputedBorder.%s" % side.ident,
@ -3267,6 +3257,8 @@ fn static_assert() {
              I::IntoIter: ExactSizeIterator
    {
        use gecko_bindings::structs::nsCSSPropertyID::eCSSPropertyExtra_no_properties;
        use gecko_bindings::structs::nsCSSPropertyID::eCSSPropertyExtra_variable;
        use gecko_bindings::structs::nsCSSPropertyID::eCSSProperty_UNKNOWN;
        let v = v.into_iter();
@ -3274,10 +3266,17 @@ fn static_assert() {
            self.gecko.mTransitions.ensure_len(v.len());
            self.gecko.mTransitionPropertyCount = v.len() as u32;
            for (servo, gecko) in v.zip(self.gecko.mTransitions.iter_mut()) {
                unsafe { gecko.mUnknownProperty.clear() };
                match servo {
-                    TransitionProperty::Unsupported(ref ident) => unsafe {
+                    TransitionProperty::Unsupported(ident) => {
-                        Gecko_StyleTransition_SetUnsupportedProperty(gecko, ident.0.as_ptr())
+                        gecko.mProperty = eCSSProperty_UNKNOWN;
                        gecko.mUnknownProperty.mRawPtr = ident.0.into_addrefed();
                    },
                    TransitionProperty::Custom(name) => {
                        gecko.mProperty = eCSSPropertyExtra_variable;
                        gecko.mUnknownProperty.mRawPtr = name.into_addrefed();
                    }
                    _ => gecko.mProperty = servo.to_nscsspropertyid().unwrap(),
                }
            }
@ -3307,15 +3306,24 @@ fn static_assert() {
        use gecko_bindings::structs::nsCSSPropertyID::eCSSProperty_UNKNOWN;
        let property = self.gecko.mTransitions[index].mProperty;
-        if property == eCSSProperty_UNKNOWN || property == eCSSPropertyExtra_variable {
+        if property == eCSSProperty_UNKNOWN {
            let atom = self.gecko.mTransitions[index].mUnknownProperty.mRawPtr;
            debug_assert!(!atom.is_null());
            TransitionProperty::Unsupported(CustomIdent(unsafe{
                Atom::from_raw(atom)
            }))
        } else if property == eCSSPropertyExtra_variable {
            let atom = self.gecko.mTransitions[index].mUnknownProperty.mRawPtr;
            debug_assert!(!atom.is_null());
            TransitionProperty::Custom(unsafe{
                Atom::from_raw(atom)
            })
        } else if property == eCSSPropertyExtra_no_properties {
-            // Actually, we don't expect TransitionProperty::Unsupported also represents "none",
+            // Actually, we don't expect TransitionProperty::Unsupported also
-            // but if the caller wants to convert it, it is fine. Please use it carefully.
+            // represents "none", but if the caller wants to convert it, it is
            // fine. Please use it carefully.
            //
            // FIXME(emilio): This is a hack, is this reachable?
            TransitionProperty::Unsupported(CustomIdent(atom!("none")))
        } else {
            property.into()
@ -3336,11 +3344,12 @@ fn static_assert() {
        for (index, transition) in self.gecko.mTransitions.iter_mut().enumerate().take(count as usize) {
            transition.mProperty = other.gecko.mTransitions[index].mProperty;
            unsafe { transition.mUnknownProperty.clear() };
            if transition.mProperty == eCSSProperty_UNKNOWN ||
               transition.mProperty == eCSSPropertyExtra_variable {
                let atom = other.gecko.mTransitions[index].mUnknownProperty.mRawPtr;
                debug_assert!(!atom.is_null());
-                unsafe { Gecko_StyleTransition_SetUnsupportedProperty(transition, atom) };
+                transition.mUnknownProperty.mRawPtr = unsafe { Atom::from_raw(atom) }.into_addrefed();
            }
        }
    }
--- a/components/style/properties/helpers.mako.rs
+++ b/components/style/properties/helpers.mako.rs
@ -594,7 +594,7 @@
                        aliases.append(alias)
            %>
            % if aliases:
-            #[css(aliases = "${','.join(aliases)}")]
+            #[parse(aliases = "${','.join(aliases)}")]
            % endif
            % endif
            ${to_camel_case(variant)},
@ -809,8 +809,10 @@
        use values::generics::rect::Rect;
        use values::specified;
-        pub fn parse_value<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>)
+        pub fn parse_value<'i, 't>(
-                                   -> Result<Longhands, ParseError<'i>> {
+            context: &ParserContext,
            input: &mut Parser<'i, 't>,
        ) -> Result<Longhands, ParseError<'i>> {
            let rect = Rect::parse_with(context, input, |_c, i| {
            % if allow_quirks:
                ${parser_function}_quirky(_c, i, specified::AllowQuirks::Yes)
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@ -9,7 +9,6 @@
    from itertools import groupby
 %>
 use cssparser::Parser;
 #[cfg(feature = "gecko")] use gecko_bindings::bindings::RawServoAnimationValueMap;
 #[cfg(feature = "gecko")] use gecko_bindings::structs::RawGeckoGfxMatrix4x4;
 #[cfg(feature = "gecko")] use gecko_bindings::structs::nsCSSPropertyID;
@ -27,12 +26,12 @@ use smallvec::SmallVec;
 use std::{cmp, ptr};
 use std::mem::{self, ManuallyDrop};
 #[cfg(feature = "gecko")] use hash::FnvHashMap;
 use style_traits::{KeywordsCollectFn, ParseError, SpecifiedValueInfo};
 use super::ComputedValues;
-use values::{CSSFloat, CustomIdent};
+use values::CSSFloat;
 use values::animated::{Animate, Procedure, ToAnimatedValue, ToAnimatedZero};
 use values::animated::color::RGBA as AnimatedRGBA;
 use values::animated::effects::Filter as AnimatedFilter;
 #[cfg(feature = "gecko")] use values::computed::TransitionProperty;
 use values::computed::{Angle, CalcLengthOrPercentage};
 use values::computed::{ClipRect, Context};
 use values::computed::{Length, LengthOrPercentage, LengthOrPercentageOrAuto};
@ -70,78 +69,6 @@ pub fn nscsspropertyid_is_animatable(property: nsCSSPropertyID) -> bool {
    }
 }
 /// A given transition property, that is either `All`, a transitionable longhand property,
 /// a shorthand with at least one transitionable longhand component, or an unsupported property.
 // NB: This needs to be here because it needs all the longhands generated
 // beforehand.
 #[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue, ToCss)]
 pub enum TransitionProperty {
    /// A shorthand.
    Shorthand(ShorthandId),
    /// A longhand transitionable property.
    Longhand(LonghandId),
    /// Unrecognized property which could be any non-transitionable, custom property, or
    /// unknown property.
    Unsupported(CustomIdent),
 }
 impl TransitionProperty {
    /// Returns `all`.
    #[inline]
    pub fn all() -> Self {
        TransitionProperty::Shorthand(ShorthandId::All)
    }
    /// Parse a transition-property value.
    pub fn parse<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
        // FIXME(https://github.com/rust-lang/rust/issues/33156): remove this
        // enum and use PropertyId when stable Rust allows destructors in
        // statics.
        //
        // FIXME: This should handle aliases too.
        pub enum StaticId {
            Longhand(LonghandId),
            Shorthand(ShorthandId),
        }
        ascii_case_insensitive_phf_map! {
            static_id -> StaticId = {
                % for prop in data.shorthands:
                "${prop.name}" => StaticId::Shorthand(ShorthandId::${prop.camel_case}),
                % endfor
                % for prop in data.longhands:
                "${prop.name}" => StaticId::Longhand(LonghandId::${prop.camel_case}),
                % endfor
            }
        }
        let location = input.current_source_location();
        let ident = input.expect_ident()?;
        Ok(match static_id(&ident) {
            Some(&StaticId::Longhand(id)) => TransitionProperty::Longhand(id),
            Some(&StaticId::Shorthand(id)) => TransitionProperty::Shorthand(id),
            None => {
                TransitionProperty::Unsupported(
                    CustomIdent::from_ident(location, ident, &["none"])?,
                )
            },
        })
    }
    /// Convert TransitionProperty to nsCSSPropertyID.
    #[cfg(feature = "gecko")]
    pub fn to_nscsspropertyid(&self) -> Result<nsCSSPropertyID, ()> {
        Ok(match *self {
            TransitionProperty::Shorthand(ShorthandId::All) => {
                nsCSSPropertyID::eCSSPropertyExtra_all_properties
            }
            TransitionProperty::Shorthand(ref id) => id.to_nscsspropertyid(),
            TransitionProperty::Longhand(ref id) => id.to_nscsspropertyid(),
            TransitionProperty::Unsupported(..) => return Err(()),
        })
    }
 }
 /// Convert nsCSSPropertyID to TransitionProperty
 #[cfg(feature = "gecko")]
 #[allow(non_upper_case_globals)]
@ -168,15 +95,6 @@ impl From<nsCSSPropertyID> for TransitionProperty {
    }
 }
 impl SpecifiedValueInfo for TransitionProperty {
    fn collect_completion_keywords(f: KeywordsCollectFn) {
        // `transition-property` can actually accept all properties and
        // arbitrary identifiers, but `all` is a special one we'd like
        // to list.
        f(&["all"]);
    }
 }
 /// Returns true if this nsCSSPropertyID is one of the transitionable properties.
 #[cfg(feature = "gecko")]
 pub fn nscsspropertyid_is_transitionable(property: nsCSSPropertyID) -> bool {
--- a/components/style/properties/longhand/box.mako.rs
+++ b/components/style/properties/longhand/box.mako.rs
@ -9,8 +9,6 @@
                         inherited=False,
                         gecko_name="Display") %>
 // TODO(SimonSapin): don't parse `inline-table`, since we don't support it
 //
 // We allow "display" to apply to placeholders because we need to make the
 // placeholder pseudo-element an inline-block in the UA stylesheet in Gecko.
 ${helpers.predefined_type(
@ -19,10 +17,10 @@ ${helpers.predefined_type(
    "computed::Display::inline()",
    initial_specified_value="specified::Display::inline()",
    animation_value_type="discrete",
    needs_context=False,
    flags="APPLIES_TO_PLACEHOLDER",
    spec="https://drafts.csswg.org/css-display/#propdef-display",
-    servo_restyle_damage="rebuild_and_reflow"
+    servo_restyle_damage="rebuild_and_reflow",
    needs_context=product == "gecko"
 )}
 // FIXME(emilio): Listing all the display values here is very unfortunate, we should teach C++ to use the
@ -257,7 +255,6 @@ ${helpers.predefined_type(
    vector=True,
    allow_empty="NotInitial",
    need_index=True,
    needs_context=False,
    animation_value_type="none",
    extra_prefixes=transition_extra_prefixes,
    spec="https://drafts.csswg.org/css-transitions/#propdef-transition-property",
--- a/components/style/properties/longhand/ui.mako.rs
+++ b/components/style/properties/longhand/ui.mako.rs
@ -41,13 +41,17 @@ ${helpers.single_keyword("-moz-window-shadow", "none default menu tooltip sheet"
                         enabled_in="chrome",
                         spec="None (Nonstandard internal property)")}
-// TODO(bug 1419695) This should be hidden from content.
+${helpers.predefined_type(
-${helpers.predefined_type("-moz-window-opacity", "Opacity", "1.0", products="gecko",
+    "-moz-window-opacity",
-                          gecko_ffi_name="mWindowOpacity",
+    "Opacity",
-                          animation_value_type="ComputedValue",
+    "1.0",
-                          spec="None (Nonstandard internal property)")}
+    products="gecko",
    gecko_ffi_name="mWindowOpacity",
    animation_value_type="ComputedValue",
    spec="None (Nonstandard internal property)",
    enabled_in="chrome",
 )}
 // TODO(bug 1419695) This should be hidden from content.
 ${helpers.predefined_type(
    "-moz-window-transform",
    "Transform",
@ -56,10 +60,10 @@ ${helpers.predefined_type(
    gecko_ffi_name="mSpecifiedWindowTransform",
    flags="GETCS_NEEDS_LAYOUT_FLUSH",
    animation_value_type="ComputedValue",
-    spec="None (Nonstandard internal property)"
+    spec="None (Nonstandard internal property)",
    enabled_in="chrome",
 )}
 // TODO(bug 1419695) This should be hidden from content.
 ${helpers.predefined_type(
    "-moz-window-transform-origin",
    "TransformOrigin",
@ -69,7 +73,8 @@ ${helpers.predefined_type(
    products="gecko",
    boxed=True,
    flags="GETCS_NEEDS_LAYOUT_FLUSH",
-    spec="None (Nonstandard internal property)"
+    spec="None (Nonstandard internal property)",
    enabled_in="chrome",
 )}
 // TODO(emilio): Probably also should be hidden from content.
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@ -22,8 +22,7 @@ use std::cell::RefCell;
 use std::fmt::{self, Write};
 use std::mem::{self, ManuallyDrop};
-#[cfg(feature = "servo")] use cssparser::RGBA;
+use cssparser::{Parser, RGBA, TokenSerializationType};
 use cssparser::{CowRcStr, Parser, TokenSerializationType, serialize_identifier};
 use cssparser::ParserInput;
 #[cfg(feature = "servo")] use euclid::SideOffsets2D;
 use context::QuirksMode;
@ -45,10 +44,10 @@ use shared_lock::StylesheetGuards;
 use style_traits::{CssWriter, KeywordsCollectFn, ParseError, ParsingMode};
 use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
 use stylesheets::{CssRuleType, Origin, UrlExtraData};
 #[cfg(feature = "servo")] use values::Either;
 use values::generics::text::LineHeight;
 use values::computed;
 use values::computed::NonNegativeLength;
 use values::serialize_atom_name;
 use rule_tree::{CascadeLevel, StrongRuleNode};
 use self::computed_value_flags::*;
 use str::{CssString, CssStringBorrow, CssStringWriter};
@ -427,6 +426,17 @@ impl NonCustomPropertyId {
        MAP[self.0]
    }
    /// Get the property name.
    #[inline]
    fn name(self) -> &'static str {
        static MAP: [&'static str; ${len(data.longhands) + len(data.shorthands) + len(data.all_aliases())}] = [
            % for property in data.longhands + data.shorthands + data.all_aliases():
                "${property.name}",
            % endfor
        ];
        MAP[self.0]
    }
    #[inline]
    fn enabled_for_all_content(self) -> bool {
        ${static_non_custom_property_id_set(
@ -499,6 +509,11 @@ impl NonCustomPropertyId {
            _ => {}
        }
        self.allowed_in_ignoring_rule_type(context)
    }
    fn allowed_in_ignoring_rule_type(self, context: &ParserContext) -> bool {
        // The semantics of these are kinda hard to reason about, what follows
        // is a description of the different combinations that can happen with
        // these three sets.
@ -576,18 +591,21 @@ impl NonCustomPropertyId {
 }
 impl From<LonghandId> for NonCustomPropertyId {
    #[inline]
    fn from(id: LonghandId) -> Self {
        NonCustomPropertyId(id as usize)
    }
 }
 impl From<ShorthandId> for NonCustomPropertyId {
    #[inline]
    fn from(id: ShorthandId) -> Self {
        NonCustomPropertyId((id as usize) + ${len(data.longhands)})
    }
 }
 impl From<AliasId> for NonCustomPropertyId {
    #[inline]
    fn from(id: AliasId) -> Self {
        NonCustomPropertyId(id as usize + ${len(data.longhands) + len(data.shorthands)})
    }
@ -814,13 +832,13 @@ bitflags! {
        const APPLIES_TO_FIRST_LINE = 1 << 4;
        /// This longhand property applies to ::placeholder.
        const APPLIES_TO_PLACEHOLDER = 1 << 5;
        /// This property's getComputedStyle implementation requires layout
        /// to be flushed.
        const GETCS_NEEDS_LAYOUT_FLUSH = 1 << 6;
        /* The following flags are currently not used in Rust code, they
         * only need to be listed in corresponding properties so that
         * they can be checked in the C++ side via ServoCSSPropList.h. */
        /// This property's getComputedStyle implementation requires layout
        /// to be flushed.
        const GETCS_NEEDS_LAYOUT_FLUSH = 0;
        /// This property can be animated on the compositor.
        const CAN_ANIMATE_ON_COMPOSITOR = 0;
    }
@ -854,12 +872,9 @@ impl fmt::Debug for LonghandId {
 impl LonghandId {
    /// Get the name of this longhand property.
    #[inline]
    pub fn name(&self) -> &'static str {
-        match *self {
+        NonCustomPropertyId::from(*self).name()
            % for property in data.longhands:
                LonghandId::${property.camel_case} => "${property.name}",
            % endfor
        }
    }
    /// Returns whether the longhand property is inherited by default.
@ -1197,12 +1212,9 @@ impl ToCss for ShorthandId {
 impl ShorthandId {
    /// Get the name for this shorthand property.
    #[inline]
    pub fn name(&self) -> &'static str {
-        match *self {
+        NonCustomPropertyId::from(*self).name()
            % for property in data.shorthands:
                ShorthandId::${property.camel_case} => "${property.name}",
            % endfor
        }
    }
    /// Converts from a ShorthandId to an adequate nsCSSPropertyID.
@ -1423,11 +1435,17 @@ impl UnparsedValue {
            // As of this writing, only the base URL is used for property
            // values.
            //
-            // FIXME(emilio): These bits are slightly fishy.
+            // NOTE(emilio): we intentionally pase `None` as the rule type here.
            // If something starts depending on it, it's probably a bug, since
            // it'd change how values are parsed depending on whether we're in a
            // @keyframes rule or not, for example... So think twice about
            // whether you want to do this!
            //
            // FIXME(emilio): ParsingMode is slightly fishy...
            let context = ParserContext::new(
                Origin::Author,
                &self.url_data,
-                Some(CssRuleType::Style),
+                None,
                ParsingMode::DEFAULT,
                quirks_mode,
            );
@ -1495,8 +1513,9 @@ impl<'a> ToCss for PropertyDeclarationId<'a> {
    {
        match *self {
            PropertyDeclarationId::Longhand(id) => dest.write_str(id.name()),
-            PropertyDeclarationId::Custom(_) => {
+            PropertyDeclarationId::Custom(ref name) => {
-                serialize_identifier(&self.name(), dest)
+                dest.write_str("--")?;
                serialize_atom_name(name, dest)
            }
        }
    }
@ -1576,8 +1595,9 @@ impl ToCss for PropertyId {
            PropertyId::Shorthand(id) => dest.write_str(id.name()),
            PropertyId::LonghandAlias(id, _) => dest.write_str(id.name()),
            PropertyId::ShorthandAlias(id, _) => dest.write_str(id.name()),
-            PropertyId::Custom(_) => {
+            PropertyId::Custom(ref name) => {
-                serialize_identifier(&self.name(), dest)
+                dest.write_str("--")?;
                serialize_atom_name(name, dest)
            }
        }
    }
@ -1674,6 +1694,24 @@ impl PropertyId {
        Ok(id)
    }
    /// Parses a property name, and returns an error if it's unknown or isn't
    /// allowed in this context, ignoring the rule_type checks.
    ///
    /// This is useful for parsing stuff from CSS values, for example.
    #[inline]
    pub fn parse_ignoring_rule_type(
        name: &str,
        context: &ParserContext,
    ) -> Result<Self, ()> {
        let id = Self::parse_unchecked(name)?;
        if !id.allowed_in_ignoring_rule_type(context) {
            return Err(());
        }
        Ok(id)
    }
    /// Returns a property id from Gecko's nsCSSPropertyID.
    #[cfg(feature = "gecko")]
    #[allow(non_upper_case_globals)]
@ -1728,21 +1766,6 @@ impl PropertyId {
        }
    }
    /// Returns the name of the property without CSS escaping.
    pub fn name(&self) -> Cow<'static, str> {
        match *self {
            PropertyId::ShorthandAlias(id, _) |
            PropertyId::Shorthand(id) => id.name().into(),
            PropertyId::LonghandAlias(id, _) |
            PropertyId::Longhand(id) => id.name().into(),
            PropertyId::Custom(ref name) => {
                let mut s = String::new();
                write!(&mut s, "--{}", name).unwrap();
                s.into()
            }
        }
    }
    fn non_custom_id(&self) -> Option<NonCustomPropertyId> {
        Some(match *self {
            PropertyId::Custom(_) => return None,
@ -1787,6 +1810,16 @@ impl PropertyId {
        id.allowed_in(context)
    }
    #[inline]
    fn allowed_in_ignoring_rule_type(&self, context: &ParserContext) -> bool {
        let id = match self.non_custom_id() {
            // Custom properties are allowed everywhere
            None => return true,
            Some(id) => id,
        };
        id.allowed_in_ignoring_rule_type(context)
    }
    /// Whether the property supports the given CSS type.
    /// `ty` should a bitflags of constants in style_traits::CssType.
    pub fn supports_type(&self, ty: u8) -> bool {
@ -1995,13 +2028,13 @@ impl PropertyDeclaration {
    pub fn parse_into<'i, 't>(
        declarations: &mut SourcePropertyDeclaration,
        id: PropertyId,
        name: CowRcStr<'i>,
        context: &ParserContext,
        input: &mut Parser<'i, 't>,
    ) -> Result<(), ParseError<'i>> {
        assert!(declarations.is_empty());
        debug_assert!(id.allowed_in(context), "{:?}", id);
        let non_custom_id = id.non_custom_id();
        let start = input.state();
        match id {
            PropertyId::Custom(property_name) => {
@ -2012,7 +2045,10 @@ impl PropertyDeclaration {
                    Ok(keyword) => DeclaredValueOwned::CSSWideKeyword(keyword),
                    Err(()) => match ::custom_properties::SpecifiedValue::parse(input) {
                        Ok(value) => DeclaredValueOwned::Value(value),
-                        Err(e) => return Err(StyleParseErrorKind::new_invalid(name, e)),
+                        Err(e) => return Err(StyleParseErrorKind::new_invalid(
                            format!("--{}", property_name),
                            e,
                        )),
                    }
                };
                declarations.push(PropertyDeclaration::Custom(CustomDeclaration {
@ -2037,7 +2073,10 @@ impl PropertyDeclaration {
                            input.reset(&start);
                            let (first_token_type, css) =
                                ::custom_properties::parse_non_custom_with_var(input).map_err(|e| {
-                                    StyleParseErrorKind::new_invalid(name, e)
+                                    StyleParseErrorKind::new_invalid(
                                        non_custom_id.unwrap().name(),
                                        e,
                                    )
                                })?;
                            Ok(PropertyDeclaration::WithVariables(VariableDeclaration {
                                id,
@ -2049,7 +2088,10 @@ impl PropertyDeclaration {
                                }),
                            }))
                        } else {
-                            Err(StyleParseErrorKind::new_invalid(name, err))
+                            Err(StyleParseErrorKind::new_invalid(
                                non_custom_id.unwrap().name(),
                                err,
                            ))
                        }
                    })
                }).map(|declaration| {
@ -2083,7 +2125,10 @@ impl PropertyDeclaration {
                            input.reset(&start);
                            let (first_token_type, css) =
                                ::custom_properties::parse_non_custom_with_var(input).map_err(|e| {
-                                    StyleParseErrorKind::new_invalid(name, e)
+                                    StyleParseErrorKind::new_invalid(
                                        non_custom_id.unwrap().name(),
                                        e,
                                    )
                                })?;
                            let unparsed = Arc::new(UnparsedValue {
                                css: css.into_owned(),
@ -2105,7 +2150,10 @@ impl PropertyDeclaration {
                            }
                            Ok(())
                        } else {
-                            Err(StyleParseErrorKind::new_invalid(name, err))
+                            Err(StyleParseErrorKind::new_invalid(
                                non_custom_id.unwrap().name(),
                                err,
                            ))
                        }
                    })
                }
@ -2453,6 +2501,7 @@ pub mod style_structs {
            /// Whether this is a multicol style.
            #[cfg(feature = "servo")]
            pub fn is_multicol(&self) -> bool {
                use values::Either;
                match self.column_width {
                    Either::First(_width) => true,
                    Either::Second(_auto) => !self.column_count.is_auto(),
@ -2564,6 +2613,59 @@ impl ComputedValues {
    pub fn custom_properties(&self) -> Option<<&Arc<::custom_properties::CustomPropertiesMap>> {
        self.custom_properties.as_ref()
    }
    /// Writes the value of the given longhand as a string in `dest`.
    ///
    /// Note that the value will usually be the computed value, except for
    /// colors, where it's resolved.
    pub fn get_longhand_property_value<W>(
        &self,
        property_id: LonghandId,
        dest: &mut CssWriter<W>
    ) -> fmt::Result
    where
        W: Write,
    {
        // TODO(emilio): Is it worth to merge branches here just like
        // PropertyDeclaration::to_css does?
        //
        // We'd need to get a concept of ~resolved value, which may not be worth
        // it.
        match property_id {
            % for prop in data.longhands:
            LonghandId::${prop.camel_case} => {
                let style_struct =
                    self.get_${prop.style_struct.ident.strip("_")}();
                let value =
                    style_struct
                    % if prop.logical:
                    .clone_${prop.ident}(self.writing_mode);
                    % else:
                    .clone_${prop.ident}();
                    % endif
                % if prop.predefined_type == "Color":
                let value = self.resolve_color(value);
                % endif
                value.to_css(dest)
            }
            % endfor
        }
    }
    /// Resolves the currentColor keyword.
    ///
    /// Any color value from computed values (except for the 'color' property
    /// itself) should go through this method.
    ///
    /// Usage example:
    /// let top_color =
    ///   style.resolve_color(style.get_border().clone_border_top_color());
    #[inline]
    pub fn resolve_color(&self, color: computed::Color) -> RGBA {
        color.to_rgba(self.get_color().clone_color())
    }
 }
 #[cfg(feature = "servo")]
@ -2598,6 +2700,26 @@ impl ComputedValues {
    /// Get the initial computed values.
    pub fn initial_values() -> &'static Self { &*INITIAL_SERVO_VALUES }
    /// Serializes the computed value of this property as a string.
    pub fn computed_value_to_string(&self, property: PropertyDeclarationId) -> String {
        match property {
            PropertyDeclarationId::Longhand(id) => {
                let mut s = String::new();
                self.get_longhand_property_value(
                    id,
                    &mut CssWriter::new(&mut s)
                ).unwrap();
                s
            }
            PropertyDeclarationId::Custom(name) => {
                self.custom_properties
                    .as_ref()
                    .and_then(|map| map.get(name))
                    .map_or(String::new(), |value| value.to_css_string())
            }
        }
    }
 }
 #[cfg(feature = "servo")]
@ -2676,18 +2798,6 @@ impl ComputedValuesInner {
        self.get_column().is_multicol()
    }
    /// Resolves the currentColor keyword.
    ///
    /// Any color value from computed values (except for the 'color' property
    /// itself) should go through this method.
    ///
    /// Usage example:
    /// let top_color = style.resolve_color(style.Border.border_top_color);
    #[inline]
    pub fn resolve_color(&self, color: computed::Color) -> RGBA {
        color.to_rgba(self.get_color().color)
    }
    /// Get the logical computed inline size.
    #[inline]
    pub fn content_inline_size(&self) -> computed::LengthOrPercentageOrAuto {
@ -2848,26 +2958,6 @@ impl ComputedValuesInner {
        // Neither perspective nor transform present
        false
    }
    /// Serializes the computed value of this property as a string.
    pub fn computed_value_to_string(&self, property: PropertyDeclarationId) -> String {
        match property {
            % for style_struct in data.active_style_structs():
                % for longhand in style_struct.longhands:
                    PropertyDeclarationId::Longhand(LonghandId::${longhand.camel_case}) => {
                        self.${style_struct.ident}.${longhand.ident}.to_css_string()
                    }
                % endfor
            % endfor
            PropertyDeclarationId::Custom(name) => {
                self.custom_properties
                    .as_ref()
                    .and_then(|map| map.get(name))
                    .map(|value| value.to_css_string())
                    .unwrap_or(String::new())
            }
        }
    }
 }
 % if product == "gecko":
--- a/components/style/properties/shorthand/box.mako.rs
+++ b/components/style/properties/shorthand/box.mako.rs
@ -123,9 +123,11 @@ macro_rules! try_parse_one {
                                    transition-timing-function
                                    transition-delay"
                    spec="https://drafts.csswg.org/css-transitions/#propdef-transition">
    use parser::Parse;
    % for prop in "delay duration property timing_function".split():
    use properties::longhands::transition_${prop};
    % endfor
    use values::specified::TransitionProperty;
    pub fn parse_value<'i, 't>(
        context: &ParserContext,
@ -137,7 +139,7 @@ macro_rules! try_parse_one {
            % endfor
            // Unlike other properties, transition-property uses an Option<> to
            // represent 'none' as `None`.
-            transition_property: Option<transition_property::SingleSpecifiedValue>,
+            transition_property: Option<TransitionProperty>,
        }
        fn parse_one_transition<'i, 't>(
@ -158,10 +160,12 @@ macro_rules! try_parse_one {
                // Must check 'transition-property' after 'transition-timing-function' since
                // 'transition-property' accepts any keyword.
                if property.is_none() {
-                    if let Ok(value) = input.try(|i| transition_property::SingleSpecifiedValue::parse(i)) {
+                    if let Ok(value) = input.try(|i| TransitionProperty::parse(context, i)) {
                        property = Some(Some(value));
                        continue;
-                    } else if input.try(|i| i.expect_ident_matching("none")).is_ok() {
+                    }
                    if input.try(|i| i.expect_ident_matching("none")).is_ok() {
                        // 'none' is not a valid value for <single-transition-property>,
                        // so it's not acceptable in the function above.
                        property = Some(None);
--- a/components/style/style_adjuster.rs
+++ b/components/style/style_adjuster.rs
@ -315,39 +315,6 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
        }
    }
    #[cfg(feature = "gecko")]
    fn adjust_for_contain(&mut self) {
        use properties::longhands::contain::SpecifiedValue;
        // An element with contain: paint needs to be a formatting context, and
        // also implies overflow: clip.
        //
        // TODO(emilio): This mimics Gecko, but spec links are missing!
        let contain = self.style.get_box().clone_contain();
        if !contain.contains(SpecifiedValue::PAINT) {
            return;
        }
        if self.style.get_box().clone_display() == Display::Inline {
            self.style
                .mutate_box()
                .set_adjusted_display(Display::InlineBlock, false);
        }
        // When 'contain: paint', update overflow from 'visible' to 'clip'.
        if self.style
            .get_box()
            .clone_contain()
            .contains(SpecifiedValue::PAINT)
        {
            if self.style.get_box().clone_overflow_x() == Overflow::Visible {
                let box_style = self.style.mutate_box();
                box_style.set_overflow_x(Overflow::MozHiddenUnscrollable);
                box_style.set_overflow_y(Overflow::MozHiddenUnscrollable);
            }
        }
    }
    /// When mathvariant is not "none", font-weight and font-style are
    /// both forced to "normal".
    #[cfg(feature = "gecko")]
@ -752,7 +719,6 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
        #[cfg(feature = "gecko")]
        {
            self.adjust_for_table_text_align();
            self.adjust_for_contain();
            self.adjust_for_mathvariant();
            self.adjust_for_justify_items();
        }
--- a/components/style/stylesheets/keyframes_rule.rs
+++ b/components/style/stylesheets/keyframes_rule.rs
@ -623,12 +623,12 @@ impl<'a, 'b, 'i> DeclarationParser<'i> for KeyframeDeclarationParser<'a, 'b> {
        let id = match PropertyId::parse(&name, self.context) {
            Ok(id) => id,
            Err(()) => return Err(input.new_custom_error(
-                StyleParseErrorKind::UnknownProperty(name.clone())
+                StyleParseErrorKind::UnknownProperty(name)
            )),
        };
        // TODO(emilio): Shouldn't this use parse_entirely?
-        PropertyDeclaration::parse_into(self.declarations, id, name, self.context, input)?;
+        PropertyDeclaration::parse_into(self.declarations, id, self.context, input)?;
        // In case there is still unparsed text in the declaration, we should
        // roll back.
--- a/components/style/stylesheets/supports_rule.rs
+++ b/components/style/stylesheets/supports_rule.rs
@ -316,20 +316,23 @@ impl Declaration {
        let mut input = ParserInput::new(&self.0);
        let mut input = Parser::new(&mut input);
        input.parse_entirely(|input| -> Result<(), CssParseError<()>> {
-                let prop = input.expect_ident_cloned().unwrap();
+            let prop = input.expect_ident_cloned().unwrap();
-                input.expect_colon().unwrap();
+            input.expect_colon().unwrap();
-                let id = PropertyId::parse(&prop, context)
+            let id = PropertyId::parse(&prop, context)
-                    .map_err(|_| input.new_custom_error(()))?;
+                .map_err(|_| input.new_custom_error(()))?;
-                let mut declarations = SourcePropertyDeclaration::new();
+            let mut declarations = SourcePropertyDeclaration::new();
-                input.parse_until_before(Delimiter::Bang, |input| {
+            input.parse_until_before(Delimiter::Bang, |input| {
-                    PropertyDeclaration::parse_into(&mut declarations, id, prop, &context, input)
+                PropertyDeclaration::parse_into(
-                        .map_err(|_| input.new_custom_error(()))
+                    &mut declarations,
-                })?;
+                    id,
-                let _ = input.try(parse_important);
+                    &context,
-                Ok(())
+                    input,
-            })
+                ).map_err(|_| input.new_custom_error(()))
-            .is_ok()
+            })?;
            let _ = input.try(parse_important);
            Ok(())
        }).is_ok()
    }
 }
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@ -1951,14 +1951,9 @@ pub struct CascadeData {
    /// cascade level.
    normal_rules: ElementAndPseudoRules,
-    /// The `:host` pseudo rules that are the rightmost selector.
+    /// The `:host` pseudo rules that are the rightmost selector (without
-    ///
+    /// accounting for pseudo-elements).
-    /// Note that as of right now these can't affect invalidation in any way,
+    host_rules: Option<Box<ElementAndPseudoRules>>,
    /// until we support the :host(<selector>) notation.
    ///
    /// Also, note that other engines don't accept stuff like :host::before /
    /// :host::after, so we don't need to store pseudo rules at all.
    host_rules: Option<Box<SelectorMap<Rule>>>,
    /// The data coming from ::slotted() pseudo-element rules.
    ///
@ -2122,11 +2117,7 @@ impl CascadeData {
    #[inline]
    fn host_rules(&self, pseudo: Option<&PseudoElement>) -> Option<&SelectorMap<Rule>> {
-        if pseudo.is_some() {
+        self.host_rules.as_ref().and_then(|d| d.rules(pseudo))
            return None;
        }
        self.host_rules.as_ref().map(|rules| &**rules)
    }
    #[inline]
@ -2258,20 +2249,20 @@ impl CascadeData {
                            }
                        }
-                        if selector.is_featureless_host_selector() {
+                        // NOTE(emilio): It's fine to look at :host and then at
-                            let host_rules = self.host_rules
+                        // ::slotted(..), since :host::slotted(..) could never
-                                .get_or_insert_with(|| Box::new(Default::default()));
+                        // possibly match, as <slot> is not a valid shadow host.
-                            host_rules.insert(rule, quirks_mode)?;
+                        let rules = if selector.is_featureless_host_selector_or_pseudo_element() {
                            self.host_rules
                                .get_or_insert_with(|| Box::new(Default::default()))
                        } else if selector.is_slotted() {
                            self.slotted_rules
                                .get_or_insert_with(|| Box::new(Default::default()))
                        } else {
-                            let rules = if selector.is_slotted() {
+                            &mut self.normal_rules
-                                self.slotted_rules
+                        };
                                    .get_or_insert_with(|| Box::new(Default::default()))
                            } else {
                                &mut self.normal_rules
                            };
-                            rules.insert(rule, pseudo_element, quirks_mode)?;
+                        rules.insert(rule, pseudo_element, quirks_mode)?;
                        }
                    }
                    self.rules_source_order += 1;
                },
--- a/components/style/values/animated/color.rs
+++ b/components/style/values/animated/color.rs
@ -6,6 +6,7 @@
 use values::animated::{Animate, Procedure, ToAnimatedZero};
 use values::distance::{ComputeSquaredDistance, SquaredDistance};
 use values::generics::color::{Color as GenericColor, ComplexColorRatios};
 /// An animated RGBA color.
 ///
@ -91,42 +92,26 @@ impl ComputeSquaredDistance for RGBA {
    }
 }
-#[allow(missing_docs)]
+/// An animated value for `<color>`.
-#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub type Color = GenericColor<RGBA>;
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Color {
    pub color: RGBA,
    pub foreground_ratio: f32,
 }
 impl Color {
    fn currentcolor() -> Self {
        Color {
            color: RGBA::transparent(),
            foreground_ratio: 1.,
        }
    }
    /// Returns a transparent intermediate color.
    pub fn transparent() -> Self {
        Color {
            color: RGBA::transparent(),
            foreground_ratio: 0.,
        }
    }
    fn is_currentcolor(&self) -> bool {
        self.foreground_ratio >= 1.
    }
    fn is_numeric(&self) -> bool {
        self.foreground_ratio <= 0.
    }
    fn effective_intermediate_rgba(&self) -> RGBA {
-        RGBA {
+        match *self {
-            alpha: self.color.alpha * (1. - self.foreground_ratio),
+            GenericColor::Numeric(color) => color,
-            ..self.color
+            GenericColor::Foreground => RGBA::transparent(),
            GenericColor::Complex(color, ratios) => RGBA {
                alpha: color.alpha * ratios.bg,
                ..color.clone()
            },
        }
    }
    fn effective_ratios(&self) -> ComplexColorRatios {
        match *self {
            GenericColor::Numeric(..) => ComplexColorRatios::NUMERIC,
            GenericColor::Foreground => ComplexColorRatios::FOREGROUND,
            GenericColor::Complex(.., ratios) => ratios,
        }
    }
 }
@ -134,80 +119,88 @@ impl Color {
 impl Animate for Color {
    #[inline]
    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
        use self::GenericColor::*;
        // Common cases are interpolating between two numeric colors,
        // two currentcolors, and a numeric color and a currentcolor.
        //
        // Note: this algorithm assumes self_portion + other_portion
        // equals to one, so it may be broken for additive operation.
        // To properly support additive color interpolation, we would
        // need two ratio fields in computed color types.
        let (this_weight, other_weight) = procedure.weights();
-        if self.foreground_ratio == other.foreground_ratio {
+
-            if self.is_currentcolor() {
+        Ok(match (*self, *other, procedure) {
-                Ok(Color::currentcolor())
+            // Any interpolation of currentColor with currentColor returns currentColor.
-            } else {
+            (Foreground, Foreground, Procedure::Interpolate { .. }) => Color::currentcolor(),
-                Ok(Color {
+            // Animating two numeric colors.
-                    color: self.color.animate(&other.color, procedure)?,
+            (Numeric(c1), Numeric(c2), _) => Numeric(c1.animate(&c2, procedure)?),
-                    foreground_ratio: self.foreground_ratio,
+            // Combinations of numeric color and currentColor
-                })
+            (Foreground, Numeric(color), _) => Self::with_ratios(
-            }
+                color,
-        } else if self.is_currentcolor() && other.is_numeric() {
+                ComplexColorRatios {
-            Ok(Color {
+                    bg: other_weight as f32,
-                color: other.color,
+                    fg: this_weight as f32,
                foreground_ratio: this_weight as f32,
            })
        } else if self.is_numeric() && other.is_currentcolor() {
            Ok(Color {
                color: self.color,
                foreground_ratio: other_weight as f32,
            })
        } else {
            // For interpolating between two complex colors, we need to
            // generate colors with effective alpha value.
            let self_color = self.effective_intermediate_rgba();
            let other_color = other.effective_intermediate_rgba();
            let color = self_color.animate(&other_color, procedure)?;
            // Then we compute the final foreground ratio, and derive
            // the final alpha value from the effective alpha value.
            let foreground_ratio = self.foreground_ratio
                .animate(&other.foreground_ratio, procedure)?;
            let alpha = color.alpha / (1. - foreground_ratio);
            Ok(Color {
                color: RGBA {
                    alpha: alpha,
                    ..color
                },
-                foreground_ratio: foreground_ratio,
+            ),
-            })
+            (Numeric(color), Foreground, _) => Self::with_ratios(
-        }
+                color,
                ComplexColorRatios {
                    bg: this_weight as f32,
                    fg: other_weight as f32,
                },
            ),
            // Any other animation of currentColor with currentColor.
            (Foreground, Foreground, _) => Self::with_ratios(
                RGBA::transparent(),
                ComplexColorRatios {
                    bg: 0.,
                    fg: (this_weight + other_weight) as f32,
                },
            ),
            // Defer to complex calculations
            _ => {
                // For interpolating between two complex colors, we need to
                // generate colors with effective alpha value.
                let self_color = self.effective_intermediate_rgba();
                let other_color = other.effective_intermediate_rgba();
                let color = self_color.animate(&other_color, procedure)?;
                // Then we compute the final background ratio, and derive
                // the final alpha value from the effective alpha value.
                let self_ratios = self.effective_ratios();
                let other_ratios = other.effective_ratios();
                let ratios = self_ratios.animate(&other_ratios, procedure)?;
                let alpha = color.alpha / ratios.bg;
                let color = RGBA { alpha, ..color };
                Self::with_ratios(color, ratios)
            }
        })
    }
 }
 impl ComputeSquaredDistance for Color {
    #[inline]
    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
        use self::GenericColor::*;
        // All comments from the Animate impl also applies here.
-        if self.foreground_ratio == other.foreground_ratio {
+        Ok(match (*self, *other) {
-            if self.is_currentcolor() {
+            (Foreground, Foreground) => SquaredDistance::from_sqrt(0.),
-                Ok(SquaredDistance::from_sqrt(0.))
+            (Numeric(c1), Numeric(c2)) => c1.compute_squared_distance(&c2)?,
-            } else {
+            (Foreground, Numeric(color)) | (Numeric(color), Foreground) => {
-                self.color.compute_squared_distance(&other.color)
+                // `computed_squared_distance` is symmetic.
                color.compute_squared_distance(&RGBA::transparent())?
                    + SquaredDistance::from_sqrt(1.)
            }
-        } else if self.is_currentcolor() && other.is_numeric() {
+            (_, _) => {
-            Ok(
+                let self_color = self.effective_intermediate_rgba();
-                RGBA::transparent().compute_squared_distance(&other.color)? +
+                let other_color = other.effective_intermediate_rgba();
-                    SquaredDistance::from_sqrt(1.),
+                let self_ratios = self.effective_ratios();
-            )
+                let other_ratios = other.effective_ratios();
-        } else if self.is_numeric() && other.is_currentcolor() {
+
-            Ok(self.color.compute_squared_distance(&RGBA::transparent())? +
+                self_color.compute_squared_distance(&other_color)?
-                SquaredDistance::from_sqrt(1.))
+                    + self_ratios.bg.compute_squared_distance(&other_ratios.bg)?
-        } else {
+                    + self_ratios.fg.compute_squared_distance(&other_ratios.fg)?
-            let self_color = self.effective_intermediate_rgba();
+            }
-            let other_color = other.effective_intermediate_rgba();
+        })
            Ok(self_color.compute_squared_distance(&other_color)? +
                self.foreground_ratio
                    .compute_squared_distance(&other.foreground_ratio)?)
        }
    }
 }
--- a/components/style/values/computed/box.rs
+++ b/components/style/values/computed/box.rs
@ -11,7 +11,7 @@ use values::generics::box_::Perspective as GenericPerspective;
 use values::generics::box_::VerticalAlign as GenericVerticalAlign;
 pub use values::specified::box_::{AnimationName, Contain, Display, OverflowClipBox};
-pub use values::specified::box_::{OverscrollBehavior, ScrollSnapType, TouchAction, WillChange};
+pub use values::specified::box_::{OverscrollBehavior, ScrollSnapType, TouchAction, TransitionProperty, WillChange};
 /// A computed value for the `vertical-align` property.
 pub type VerticalAlign = GenericVerticalAlign<LengthOrPercentage>;
--- a/components/style/values/computed/color.rs
+++ b/components/style/values/computed/color.rs
@ -8,20 +8,8 @@ use cssparser::{Color as CSSParserColor, RGBA};
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
 use values::animated::ToAnimatedValue;
-use values::animated::color::{Color as AnimatedColor, RGBA as AnimatedRGBA};
+use values::animated::color::RGBA as AnimatedRGBA;
-
+use values::generics::color::Color as GenericColor;
 /// This struct represents a combined color from a numeric color and
 /// the current foreground color (currentcolor keyword).
 /// Conceptually, the formula is "color * (1 - p) + currentcolor * p"
 /// where p is foreground_ratio.
 #[derive(Clone, Copy, Debug, MallocSizeOf)]
 pub struct Color {
    /// RGBA color.
    pub color: RGBA,
    /// The ratio of currentcolor in complex color.
    pub foreground_ratio: u8,
 }
 /// Computed value type for the specified RGBAColor.
 pub type RGBAColor = RGBA;
@ -29,89 +17,49 @@ pub type RGBAColor = RGBA;
 /// The computed value of the `color` property.
 pub type ColorPropertyValue = RGBA;
-impl Color {
+/// A computed value for `<color>`.
-    /// Returns a numeric color representing the given RGBA value.
+pub type Color = GenericColor<RGBAColor>;
    pub fn rgba(rgba: RGBA) -> Color {
        Color {
            color: rgba,
            foreground_ratio: 0,
        }
    }
 impl Color {
    /// Returns a complex color value representing transparent.
    pub fn transparent() -> Color {
        Color::rgba(RGBA::transparent())
    }
    /// Returns a complex color value representing currentcolor.
    pub fn currentcolor() -> Color {
        Color {
            color: RGBA::transparent(),
            foreground_ratio: u8::max_value(),
        }
    }
    /// Whether it is a numeric color (no currentcolor component).
    pub fn is_numeric(&self) -> bool {
        self.foreground_ratio == 0
    }
    /// Whether it is a currentcolor value (no numeric color component).
    pub fn is_currentcolor(&self) -> bool {
        self.foreground_ratio == u8::max_value()
    }
    /// Combine this complex color with the given foreground color into
    /// a numeric RGBA color. It currently uses linear blending.
    pub fn to_rgba(&self, fg_color: RGBA) -> RGBA {
-        // Common cases that the complex color is either pure numeric
+        let (color, ratios) = match *self {
-        // color or pure currentcolor.
+            // Common cases that the complex color is either pure numeric
-        if self.is_numeric() {
+            // color or pure currentcolor.
-            return self.color;
+            GenericColor::Numeric(color) => return color,
-        }
+            GenericColor::Foreground => return fg_color,
-        if self.is_currentcolor() {
+            GenericColor::Complex(color, ratios) => (color, ratios),
-            return fg_color.clone();
+        };
        }
        fn blend_color_component(bg: u8, fg: u8, fg_alpha: u8) -> u8 {
            let bg_ratio = (u8::max_value() - fg_alpha) as u32;
            let fg_ratio = fg_alpha as u32;
            let color = bg as u32 * bg_ratio + fg as u32 * fg_ratio;
            // Rounding divide the number by 255
            ((color + 127) / 255) as u8
        }
        // Common case that alpha channel is equal (usually both are opaque).
        let fg_ratio = self.foreground_ratio;
        if self.color.alpha == fg_color.alpha {
            let r = blend_color_component(self.color.red, fg_color.red, fg_ratio);
            let g = blend_color_component(self.color.green, fg_color.green, fg_ratio);
            let b = blend_color_component(self.color.blue, fg_color.blue, fg_ratio);
            return RGBA::new(r, g, b, fg_color.alpha);
        }
        // For the more complicated case that the alpha value differs,
        // we use the following formula to compute the components:
-        // alpha = self_alpha * (1 - fg_ratio) + fg_alpha * fg_ratio
+        // alpha = self_alpha * bg_ratio + fg_alpha * fg_ratio
-        // color = (self_color * self_alpha * (1 - fg_ratio) +
+        // color = (self_color * self_alpha * bg_ratio +
        //          fg_color * fg_alpha * fg_ratio) / alpha
-        let p1 = (1. / 255.) * (255 - fg_ratio) as f32;
+        let p1 = ratios.bg;
-        let a1 = self.color.alpha_f32();
+        let a1 = color.alpha_f32();
-        let r1 = a1 * self.color.red_f32();
+        let r1 = a1 * color.red_f32();
-        let g1 = a1 * self.color.green_f32();
+        let g1 = a1 * color.green_f32();
-        let b1 = a1 * self.color.blue_f32();
+        let b1 = a1 * color.blue_f32();
-        let p2 = 1. - p1;
+        let p2 = ratios.fg;
        let a2 = fg_color.alpha_f32();
        let r2 = a2 * fg_color.red_f32();
        let g2 = a2 * fg_color.green_f32();
        let b2 = a2 * fg_color.blue_f32();
        let a = p1 * a1 + p2 * a2;
-        if a == 0.0 {
+        if a <= 0. {
            return RGBA::transparent();
        }
        let a = f32::min(a, 1.);
        let inverse_a = 1. / a;
        let r = (p1 * r1 + p2 * r2) * inverse_a;
@ -121,53 +69,15 @@ impl Color {
    }
 }
 impl PartialEq for Color {
    fn eq(&self, other: &Color) -> bool {
        self.foreground_ratio == other.foreground_ratio &&
            (self.is_currentcolor() || self.color == other.color)
    }
 }
 impl From<RGBA> for Color {
    fn from(color: RGBA) -> Color {
        Color {
            color: color,
            foreground_ratio: 0,
        }
    }
 }
 impl ToCss for Color {
    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    where
        W: fmt::Write,
    {
-        if self.is_numeric() {
+        match *self {
-            self.color.to_css(dest)
+            GenericColor::Numeric(color) => color.to_css(dest),
-        } else if self.is_currentcolor() {
+            GenericColor::Foreground => CSSParserColor::CurrentColor.to_css(dest),
-            CSSParserColor::CurrentColor.to_css(dest)
+            _ => Ok(()),
        } else {
            Ok(())
        }
    }
 }
 impl ToAnimatedValue for Color {
    type AnimatedValue = AnimatedColor;
    #[inline]
    fn to_animated_value(self) -> Self::AnimatedValue {
        AnimatedColor {
            color: self.color.to_animated_value(),
            foreground_ratio: self.foreground_ratio as f32 * (1. / 255.),
        }
    }
    #[inline]
    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
        Color {
            color: RGBA::from_animated_value(animated.color),
            foreground_ratio: (animated.foreground_ratio * 255.).round() as u8,
        }
    }
 }
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@ -30,7 +30,6 @@ use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent
 use super::specified;
 pub use app_units::Au;
 pub use properties::animated_properties::TransitionProperty;
 #[cfg(feature = "gecko")]
 pub use self::align::{AlignContent, AlignItems, JustifyContent, JustifyItems, SelfAlignment};
 #[cfg(feature = "gecko")]
@ -43,7 +42,7 @@ pub use self::font::{FontSize, FontSizeAdjust, FontStretch, FontSynthesis, FontV
 pub use self::font::{FontFamily, FontLanguageOverride, FontStyle, FontVariantEastAsian, FontVariationSettings};
 pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumeric};
 pub use self::font::{MozScriptLevel, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
-pub use self::box_::{AnimationIterationCount, AnimationName, Contain, Display};
+pub use self::box_::{AnimationIterationCount, AnimationName, Contain, Display, TransitionProperty};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective};
 pub use self::box_::{ScrollSnapType, TouchAction, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorPropertyValue, RGBAColor};
--- a/components/style/values/generics/color.rs
+++ b/components/style/values/generics/color.rs
@ -0,0 +1,76 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 //! Generic types for color properties.
 /// Ratios representing the contribution of color and currentcolor to
 /// the final color value.
 #[derive(Animate, Clone, Copy, Debug, MallocSizeOf, PartialEq, ToAnimatedValue)]
 pub struct ComplexColorRatios {
    /// Numeric color contribution.
    pub bg: f32,
    /// Foreground color, aka currentcolor, contribution.
    pub fg: f32,
 }
 impl ComplexColorRatios {
    /// Ratios representing a `Numeric` color.
    pub const NUMERIC: ComplexColorRatios = ComplexColorRatios { bg: 1., fg: 0. };
    /// Ratios representing the `Foreground` color.
    pub const FOREGROUND: ComplexColorRatios = ComplexColorRatios { bg: 0., fg: 1. };
 }
 /// This enum represents a combined color from a numeric color and
 /// the current foreground color (currentcolor keyword).
 #[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToAnimatedValue)]
 pub enum Color<RGBA> {
    ///  Numeric RGBA color.
    Numeric(RGBA),
    /// The current foreground color.
    Foreground,
    /// A linear combination of numeric color and currentcolor.
    /// The formula is: `color * ratios.bg + currentcolor * ratios.fg`.
    Complex(RGBA, ComplexColorRatios),
 }
 impl<RGBA> Color<RGBA> {
    /// Create a color based upon the specified ratios.
    pub fn with_ratios(color: RGBA, ratios: ComplexColorRatios) -> Self {
        if ratios == ComplexColorRatios::NUMERIC {
            Color::Numeric(color)
        } else if ratios == ComplexColorRatios::FOREGROUND {
            Color::Foreground
        } else {
            Color::Complex(color, ratios)
        }
    }
    /// Returns a numeric color representing the given RGBA value.
    pub fn rgba(color: RGBA) -> Self {
        Color::Numeric(color)
    }
    /// Returns a complex color value representing currentcolor.
    pub fn currentcolor() -> Self {
        Color::Foreground
    }
    /// Whether it is a numeric color (no currentcolor component).
    pub fn is_numeric(&self) -> bool {
        matches!(*self, Color::Numeric(..))
    }
    /// Whether it is a currentcolor value (no numeric color component).
    pub fn is_currentcolor(&self) -> bool {
        matches!(*self, Color::Foreground)
    }
 }
 impl<RGBA> From<RGBA> for Color<RGBA> {
    fn from(color: RGBA) -> Self {
        Self::rgba(color)
    }
 }
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@ -17,6 +17,7 @@ pub mod basic_shape;
 pub mod border;
 #[path = "box.rs"]
 pub mod box_;
 pub mod color;
 pub mod column;
 pub mod counters;
 pub mod effects;
--- a/components/style/values/mod.rs
+++ b/components/style/values/mod.rs
@ -9,7 +9,7 @@
 #![deny(missing_docs)]
 use Atom;
-pub use cssparser::{serialize_identifier, CowRcStr, Parser, SourceLocation, Token, RGBA};
+pub use cssparser::{serialize_identifier, serialize_name, CowRcStr, Parser, SourceLocation, Token, RGBA};
 use parser::{Parse, ParserContext};
 use selectors::parser::SelectorParseErrorKind;
 use std::fmt::{self, Debug, Write};
@ -60,6 +60,28 @@ where
    serialize_identifier(&ident, dest)
 }
 /// Serialize a name which is represented as an Atom.
 #[cfg(feature = "gecko")]
 pub fn serialize_atom_name<W>(ident: &Atom, dest: &mut W) -> fmt::Result
 where
    W: Write,
 {
    ident.with_str(|s| serialize_name(s, dest))
 }
 /// Serialize a name which is represented as an Atom.
 #[cfg(feature = "servo")]
 pub fn serialize_atom_name<Static, W>(
    ident: &::string_cache::Atom<Static>,
    dest: &mut W,
 ) -> fmt::Result
 where
    Static: ::string_cache::StaticAtomSet,
    W: Write,
 {
    serialize_name(&ident, dest)
 }
 /// Serialize a normalized value into percentage.
 pub fn serialize_percentage<W>(value: CSSFloat, dest: &mut CssWriter<W>) -> fmt::Result
 where
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@ -6,11 +6,12 @@
 use Atom;
 use cssparser::Parser;
 use custom_properties::Name as CustomPropertyName;
 use parser::{Parse, ParserContext};
-use properties::{LonghandId, PropertyId, PropertyFlags, PropertyDeclarationId};
+use properties::{LonghandId, ShorthandId, PropertyId, PropertyFlags, PropertyDeclarationId};
 use selectors::parser::SelectorParseErrorKind;
 use std::fmt::{self, Write};
-use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+use style_traits::{CssWriter, KeywordsCollectFn, ParseError, StyleParseErrorKind, SpecifiedValueInfo, ToCss};
 use values::{CustomIdent, KeyframesName};
 use values::generics::box_::AnimationIterationCount as GenericAnimationIterationCount;
 use values::generics::box_::Perspective as GenericPerspective;
@ -18,6 +19,17 @@ use values::generics::box_::VerticalAlign as GenericVerticalAlign;
 use values::specified::{AllowQuirks, Number};
 use values::specified::length::{LengthOrPercentage, NonNegativeLength};
 #[cfg(feature = "gecko")]
 fn moz_display_values_enabled(context: &ParserContext) -> bool {
    use gecko_bindings::structs;
    use stylesheets::Origin;
    context.stylesheet_origin == Origin::UserAgent ||
    context.chrome_rules_enabled() ||
    unsafe {
        structs::StaticPrefs_sVarCache_layout_css_xul_display_values_content_enabled
    }
 }
 #[allow(missing_docs)]
 #[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq,
         SpecifiedValueInfo, ToComputedValue, ToCss)]
@ -41,9 +53,9 @@ pub enum Display {
    TableCaption,
    ListItem,
    None,
-    #[css(aliases = "-webkit-flex")]
+    #[parse(aliases = "-webkit-flex")]
    Flex,
-    #[css(aliases = "-webkit-inline-flex")]
+    #[parse(aliases = "-webkit-inline-flex")]
    InlineFlex,
    #[cfg(feature = "gecko")]
    Grid,
@ -72,22 +84,31 @@ pub enum Display {
    #[cfg(feature = "gecko")]
    MozInlineBox,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozGrid,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozInlineGrid,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozGridGroup,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozGridLine,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozStack,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozInlineStack,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozDeck,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozPopup,
    #[cfg(feature = "gecko")]
    #[parse(condition = "moz_display_values_enabled")]
    MozGroupbox,
 }
@ -444,7 +465,7 @@ fn change_bits_for_longhand(longhand: LonghandId) -> WillChangeBits {
 }
 fn change_bits_for_maybe_property(ident: &str, context: &ParserContext) -> WillChangeBits {
-    let id = match PropertyId::parse(ident, context) {
+    let id = match PropertyId::parse_ignoring_rule_type(ident, context) {
        Ok(id) => id,
        Err(..) => return WillChangeBits::empty(),
    };
@ -714,3 +735,96 @@ impl Parse for Perspective {
        )?))
    }
 }
 /// A given transition property, that is either `All`, a longhand or shorthand
 /// property, or an unsupported or custom property.
 #[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue)]
 pub enum TransitionProperty {
    /// A shorthand.
    Shorthand(ShorthandId),
    /// A longhand transitionable property.
    Longhand(LonghandId),
    /// A custom property.
    Custom(CustomPropertyName),
    /// Unrecognized property which could be any non-transitionable, custom property, or
    /// unknown property.
    Unsupported(CustomIdent),
 }
 impl ToCss for TransitionProperty {
    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    where
        W: Write,
    {
        use values::serialize_atom_name;
        match *self {
            TransitionProperty::Shorthand(ref s) => s.to_css(dest),
            TransitionProperty::Longhand(ref l) => l.to_css(dest),
            TransitionProperty::Custom(ref name) => {
                dest.write_str("--")?;
                serialize_atom_name(name, dest)
            }
            TransitionProperty::Unsupported(ref i) => i.to_css(dest),
        }
    }
 }
 impl Parse for TransitionProperty {
    fn parse<'i, 't>(
        context: &ParserContext,
        input: &mut Parser<'i, 't>,
    ) -> Result<Self, ParseError<'i>> {
        let location = input.current_source_location();
        let ident = input.expect_ident()?;
        let id = match PropertyId::parse_ignoring_rule_type(&ident, context) {
            Ok(id) => id,
            Err(..) => return Ok(TransitionProperty::Unsupported(
                CustomIdent::from_ident(location, ident, &["none"])?,
            )),
        };
        Ok(match id.as_shorthand() {
            Ok(s) => TransitionProperty::Shorthand(s),
            Err(longhand_or_custom) => {
                match longhand_or_custom {
                    PropertyDeclarationId::Longhand(id) => TransitionProperty::Longhand(id),
                    PropertyDeclarationId::Custom(custom) => {
                        TransitionProperty::Custom(custom.clone())
                    }
                }
            }
        })
    }
 }
 impl SpecifiedValueInfo for TransitionProperty {
    fn collect_completion_keywords(f: KeywordsCollectFn) {
        // `transition-property` can actually accept all properties and
        // arbitrary identifiers, but `all` is a special one we'd like
        // to list.
        f(&["all"]);
    }
 }
 impl TransitionProperty {
    /// Returns `all`.
    #[inline]
    pub fn all() -> Self {
        TransitionProperty::Shorthand(ShorthandId::All)
    }
    /// Convert TransitionProperty to nsCSSPropertyID.
    #[cfg(feature = "gecko")]
    pub fn to_nscsspropertyid(&self) -> Result<::gecko_bindings::structs::nsCSSPropertyID, ()> {
        Ok(match *self {
            TransitionProperty::Shorthand(ShorthandId::All) => {
                ::gecko_bindings::structs::nsCSSPropertyID::eCSSPropertyExtra_all_properties
            }
            TransitionProperty::Shorthand(ref id) => id.to_nscsspropertyid(),
            TransitionProperty::Longhand(ref id) => id.to_nscsspropertyid(),
            TransitionProperty::Custom(..) |
            TransitionProperty::Unsupported(..) => return Err(()),
        })
    }
 }
--- a/components/style/values/specified/color.rs
+++ b/components/style/values/specified/color.rs
@ -18,6 +18,7 @@ use style_traits::{CssType, CssWriter, KeywordsCollectFn, ParseError, StyleParse
 use style_traits::{SpecifiedValueInfo, ToCss, ValueParseErrorKind};
 use super::AllowQuirks;
 use values::computed::{Color as ComputedColor, Context, ToComputedValue};
 use values::generics::color::Color as GenericColor;
 use values::specified::calc::CalcNode;
 /// Specified color value
@ -88,11 +89,11 @@ impl<'a, 'b: 'a, 'i: 'a> ::cssparser::ColorComponentParser<'i> for ColorComponen
                };
                Ok(AngleOrNumber::Angle { degrees })
-            },
+            }
            Token::Number { value, .. } => Ok(AngleOrNumber::Number { value }),
            Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                input.parse_nested_block(|i| CalcNode::parse_angle_or_number(self.0, i))
-            },
+            }
            t => return Err(location.new_unexpected_token_error(t)),
        }
    }
@ -119,10 +120,10 @@ impl<'a, 'b: 'a, 'i: 'a> ::cssparser::ColorComponentParser<'i> for ColorComponen
            Token::Number { value, .. } => Ok(NumberOrPercentage::Number { value }),
            Token::Percentage { unit_value, .. } => {
                Ok(NumberOrPercentage::Percentage { unit_value })
-            },
+            }
            Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                input.parse_nested_block(|i| CalcNode::parse_number_or_percentage(self.0, i))
-            },
+            }
            t => return Err(location.new_unexpected_token_error(t)),
        }
    }
@ -168,10 +169,10 @@ impl Parse for Color {
                        Err(e.location.new_custom_error(StyleParseErrorKind::ValueError(
                            ValueParseErrorKind::InvalidColor(t),
                        )))
-                    },
+                    }
                    _ => Err(e),
                }
-            },
+            }
        }
    }
 }
@ -275,10 +276,10 @@ impl Color {
                }
                return parse_hash_color(ident.as_bytes())
                    .map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-            },
+            }
            ref t => {
                return Err(location.new_unexpected_token_error(t.clone()));
-            },
+            }
        };
        if value < 0 {
            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
@ -358,11 +359,11 @@ impl Color {
                        Keyword::MozVisitedhyperlinktext => pres_context.mVisitedLinkColor,
                    })
                })
-            },
+            }
            #[cfg(feature = "gecko")]
            Color::InheritFromBodyQuirk => {
                _context.map(|context| ComputedColor::rgba(context.device().body_text_color()))
-            },
+            }
        }
    }
 }
@ -372,7 +373,7 @@ impl ToComputedValue for Color {
    fn to_computed_value(&self, context: &Context) -> ComputedColor {
        let result = self.to_computed_color(Some(context)).unwrap();
-        if result.foreground_ratio != 0 {
+        if !result.is_numeric() {
            if let Some(longhand) = context.for_non_inherited_property {
                if longhand.stores_complex_colors_lossily() {
                    context.rule_cache_conditions.borrow_mut().set_uncacheable();
@ -383,12 +384,10 @@ impl ToComputedValue for Color {
    }
    fn from_computed_value(computed: &ComputedColor) -> Self {
-        if computed.is_numeric() {
+        match *computed {
-            Color::rgba(computed.color)
+            GenericColor::Numeric(color) => Color::rgba(color),
-        } else if computed.is_currentcolor() {
+            GenericColor::Foreground => Color::currentcolor(),
-            Color::currentcolor()
+            GenericColor::Complex(..) => Color::Complex(*computed),
        } else {
            Color::Complex(*computed)
        }
    }
 }
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@ -23,7 +23,6 @@ use super::generics::grid::{TrackList as GenericTrackList, TrackSize as GenericT
 use values::serialize_atom_identifier;
 use values::specified::calc::CalcNode;
 pub use properties::animated_properties::TransitionProperty;
 pub use self::angle::Angle;
 #[cfg(feature = "gecko")]
 pub use self::align::{AlignContent, AlignItems, AlignSelf, ContentDistribution};
@ -40,7 +39,7 @@ pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumer
 pub use self::font::{MozScriptLevel, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
 pub use self::box_::{AnimationIterationCount, AnimationName, Contain, Display};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective};
-pub use self::box_::{ScrollSnapType, TouchAction, VerticalAlign, WillChange};
+pub use self::box_::{ScrollSnapType, TouchAction, TransitionProperty, VerticalAlign, WillChange};
 pub use self::color::{Color, ColorPropertyValue, RGBAColor};
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset};
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};
--- a/components/style_derive/lib.rs
+++ b/components/style_derive/lib.rs
@ -40,7 +40,7 @@ pub fn derive_to_animated_value(stream: TokenStream) -> TokenStream {
    to_animated_value::derive(input).into()
 }
-#[proc_macro_derive(Parse, attributes(css))]
+#[proc_macro_derive(Parse, attributes(css, parse))]
 pub fn derive_parse(stream: TokenStream) -> TokenStream {
    let input = syn::parse(stream).unwrap();
    parse::derive(input).into()
@ -64,7 +64,7 @@ pub fn derive_to_css(stream: TokenStream) -> TokenStream {
    to_css::derive(input).into()
 }
-#[proc_macro_derive(SpecifiedValueInfo, attributes(css, value_info))]
+#[proc_macro_derive(SpecifiedValueInfo, attributes(css, parse, value_info))]
 pub fn derive_specified_value_info(stream: TokenStream) -> TokenStream {
    let input = syn::parse(stream).unwrap();
    specified_value_info::derive(input).into()
--- a/components/style_derive/parse.rs
+++ b/components/style_derive/parse.rs
@ -4,14 +4,22 @@
 use cg;
 use quote::Tokens;
-use syn::DeriveInput;
+use syn::{DeriveInput, Path};
 use synstructure;
 use to_css::CssVariantAttrs;
 #[darling(attributes(parse), default)]
 #[derive(Default, FromVariant)]
 pub struct ParseVariantAttrs {
    pub aliases: Option<String>,
    pub condition: Option<Path>,
 }
 pub fn derive(input: DeriveInput) -> Tokens {
    let name = &input.ident;
    let s = synstructure::Structure::new(&input);
    let mut saw_condition = false;
    let match_body = s.variants().iter().fold(quote!(), |match_body, variant| {
        let bindings = variant.bindings();
        assert!(
@ -19,23 +27,31 @@ pub fn derive(input: DeriveInput) -> Tokens {
            "Parse is only supported for single-variant enums for now"
        );
-        let variant_attrs = cg::parse_variant_attrs_from_ast::<CssVariantAttrs>(&variant.ast());
+        let css_variant_attrs =
-        if variant_attrs.skip {
+            cg::parse_variant_attrs_from_ast::<CssVariantAttrs>(&variant.ast());
        let parse_attrs =
            cg::parse_variant_attrs_from_ast::<ParseVariantAttrs>(&variant.ast());
        if css_variant_attrs.skip {
            return match_body;
        }
        let identifier = cg::to_css_identifier(
-            &variant_attrs.keyword.unwrap_or(variant.ast().ident.as_ref().into()),
+            &css_variant_attrs.keyword.unwrap_or(variant.ast().ident.as_ref().into()),
        );
        let ident = &variant.ast().ident;
-        let mut body = quote! {
+        saw_condition |= parse_attrs.condition.is_some();
-            #match_body
+        let condition = match parse_attrs.condition {
-            #identifier => Ok(#name::#ident),
+            Some(ref p) => quote! { if #p(context) },
            None => quote! { },
        };
        let mut body = quote! {
            #match_body
            #identifier #condition => Ok(#name::#ident),
        };
-        let aliases = match variant_attrs.aliases {
+        let aliases = match parse_attrs.aliases {
            Some(aliases) => aliases,
            None => return body,
        };
@ -43,25 +59,51 @@ pub fn derive(input: DeriveInput) -> Tokens {
        for alias in aliases.split(",") {
            body = quote! {
                #body
-                #alias => Ok(#name::#ident),
+                #alias #condition => Ok(#name::#ident),
            };
        }
        body
    });
    let context_ident = if saw_condition {
        quote! { context }
    } else {
        quote! { _ }
    };
    let parse_body = if saw_condition {
        quote! {
            let location = input.current_source_location();
            let ident = input.expect_ident()?;
            match_ignore_ascii_case! { &ident,
                #match_body
                _ => Err(location.new_unexpected_token_error(
                    ::cssparser::Token::Ident(ident.clone())
                ))
            }
        }
    } else {
        quote! { Self::parse(input) }
    };
    let parse_trait_impl = quote! {
        impl ::parser::Parse for #name {
            #[inline]
            fn parse<'i, 't>(
-                _: &::parser::ParserContext,
+                #context_ident: &::parser::ParserContext,
                input: &mut ::cssparser::Parser<'i, 't>,
            ) -> Result<Self, ::style_traits::ParseError<'i>> {
-                Self::parse(input)
+                #parse_body
            }
        }
    };
    if saw_condition {
        return parse_trait_impl;
    }
    // TODO(emilio): It'd be nice to get rid of these, but that makes the
    // conversion harder...
    let methods_impl = quote! {
--- a/components/style_derive/specified_value_info.rs
+++ b/components/style_derive/specified_value_info.rs
@ -3,6 +3,7 @@
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 use cg;
 use parse::ParseVariantAttrs;
 use quote::Tokens;
 use syn::{Data, DeriveInput, Fields, Ident, Type};
 use to_css::{CssFieldAttrs, CssInputAttrs, CssVariantAttrs};
@ -33,10 +34,11 @@ pub fn derive(mut input: DeriveInput) -> Tokens {
                for v in e.variants.iter() {
                    let css_attrs = cg::parse_variant_attrs::<CssVariantAttrs>(&v);
                    let info_attrs = cg::parse_variant_attrs::<ValueInfoVariantAttrs>(&v);
                    let parse_attrs = cg::parse_variant_attrs::<ParseVariantAttrs>(&v);
                    if css_attrs.skip {
                        continue;
                    }
-                    if let Some(aliases) = css_attrs.aliases {
+                    if let Some(aliases) = parse_attrs.aliases {
                        for alias in aliases.split(",") {
                            values.push(alias.to_string());
                        }
--- a/components/style_derive/to_css.rs
+++ b/components/style_derive/to_css.rs
@ -234,7 +234,6 @@ pub struct CssVariantAttrs {
    pub comma: bool,
    pub dimension: bool,
    pub keyword: Option<String>,
    pub aliases: Option<String>,
    pub skip: bool,
 }
--- a/components/style_traits/lib.rs
+++ b/components/style_traits/lib.rs
@ -177,7 +177,11 @@ pub enum ValueParseErrorKind<'i> {
 impl<'i> StyleParseErrorKind<'i> {
    /// Create an InvalidValue parse error
-    pub fn new_invalid(name: CowRcStr<'i>, value_error: ParseError<'i>) -> ParseError<'i> {
+    pub fn new_invalid<S>(name: S, value_error: ParseError<'i>) -> ParseError<'i>
    where
        S: Into<CowRcStr<'i>>,
    {
        let name = name.into();
        let variant = match value_error.kind {
            cssparser::ParseErrorKind::Custom(StyleParseErrorKind::ValueError(e)) => {
                match e {
--- a/components/style_traits/specified_value_info.rs
+++ b/components/style_traits/specified_value_info.rs
@ -43,7 +43,7 @@ pub type KeywordsCollectFn<'a> = &'a mut FnMut(&[&'static str]);
 ///   name is listed in `collect_completion_keywords`.
 /// * If `#[css(skip)]` is found, the content inside the variant or
 ///   field is ignored.
-/// * Values listed in `#[css(if_empty)]`, `#[css(aliases)]`, and
+/// * Values listed in `#[css(if_empty)]`, `#[parse(aliases)]`, and
 ///   `#[css(keyword)]` are added into `collect_completion_keywords`.
 ///
 /// In addition to `css` attributes, it also has `value_info` helper
--- a/servo-tidy.toml
+++ b/servo-tidy.toml
@ -39,13 +39,9 @@ num = [
 # Ignored packages with duplicated versions
 packages = [
  "bitflags",
  "itoa",
  "log",
  "num-traits",
  "quote",
  "rand",
  "syn",
  "unicode-xid",
  "winapi",
 ]
 # Files that are ignored for all tidy and lint checks.
--- a/tests/wpt/metadata/css/css-transitions/currentcolor-animation-001.html.ini
+++ b/tests/wpt/metadata/css/css-transitions/currentcolor-animation-001.html.ini
@ -1,5 +0,0 @@
 [currentcolor-animation-001.html]
  type: testharness
  [currentcolortransition]
    expected: FAIL