Update WR (clip scroll group work).

This shouldn't have any noticeable change on Servo, but as we land
various parts of the clip/scroll changes, keeping Servo up to date
will hopefully help catch any regressions early.

Cargo.lock

@@ -3208,7 +3208,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.17.0"
-source = "git+https://github.com/servo/webrender#bcd9ed5e74d657b3c9b6d62996e84c1a3ee7141b"
+source = "git+https://github.com/servo/webrender#12e583107f5525012f838acf847b2d9b47ea3f60"
 dependencies = [
  "app_units 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "bincode 1.0.0-alpha2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3236,7 +3236,7 @@ dependencies = [
 [[package]]
 name = "webrender_traits"
 version = "0.16.0"
-source = "git+https://github.com/servo/webrender#bcd9ed5e74d657b3c9b6d62996e84c1a3ee7141b"
+source = "git+https://github.com/servo/webrender#12e583107f5525012f838acf847b2d9b47ea3f60"
 dependencies = [
  "app_units 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",

tests/wpt/metadata-css/compositing-1_dev/html/mix-blend-mode-blended-element-overflow-scroll.htm.ini

@@ -1,3 +1,5 @@
 [mix-blend-mode-blended-element-overflow-scroll.htm]
   type: reftest
-  expected: FAIL
+  expected:
+    if os == "linux": FAIL
+

tests/wpt/metadata-css/compositing-1_dev/html/mix-blend-mode-iframe-parent.htm.ini

@@ -1,3 +1,5 @@
 [mix-blend-mode-iframe-parent.htm]
   type: reftest
-  expected: FAIL
+  expected:
+    if os == "linux": FAIL
+

tests/wpt/metadata-css/compositing-1_dev/html/mix-blend-mode-iframe-sibling.htm.ini

@@ -1,3 +1,5 @@
 [mix-blend-mode-iframe-sibling.htm]
   type: reftest
-  expected: FAIL
+  expected:
+    if os == "linux": FAIL
+