Auto merge of #14038 - upsuper:bug1294299, r=heycam

Add Element.style support for stylo

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This is the Servo side change of [bug 1294299](https://bugzilla.mozilla.org/show_bug.cgi?id=1294299) which has been reviewed by @heycam, @emilio, and @SimonSapin.

This should not be merged until the Gecko side change gets merged into mozilla-central.

r? @heycam

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/style/binding_tools/regen.py

@@ -236,10 +236,12 @@ COMPILATION_TARGETS = {
         "target_dir": "../gecko_bindings",
         "blacklist_types": [
             "nsACString_internal",
+            "nsAString_internal",
         ],
         "raw_lines": [
-            "pub use nsstring::nsACString;",
+            "pub use nsstring::{nsACString, nsAString};",
             "type nsACString_internal = nsACString;",
+            "type nsAString_internal = nsAString;"
         ],
         "flags": [
             "--ignore-methods",