WR multi-document update - try 2
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Combines #17892 with the patch to detach style_traits from webrender_api
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WR multi-document update
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The PR updates WR version to support multiple documents (https://github.com/servo/webrender/pull/1509) but doesn't take advantage of this new feature yet.
It also makes Servo to use `DevicePixel` from WR instead of rolling out another one.
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style: Remove now-unused empty Variables struct.
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The `Servo_GetEmptyVariables` FFI function no longer has any callers from Gecko, so we can remove it and the code that creates/frees that struct.
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Add message suffixes to stylo error reports.
This is the Servo-side part of https://bugzilla.mozilla.org/show_bug.cgi?id=1381137. This allows us to add the "Declaration dropped" or "Skipped to next declaration" messages after relevant CSS errors that are reported.
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It makes just no sense, and I'd rather not complicate the logic in the traversal
implementations, seems easy to just handle it here.
MozReview-Commit-ID: 3PnT2Jyta8g
Store COW strings in CSS parser errors when possible.
This should be a straightforward performance improvement in pages with lots of CSS property values that the parser does not understand.
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Replace all uses of the style::stylearc alias with servo_arc.
The `stylearc` alias is left there temporarilly and will be removed completely in a later commit/PR where also `components/style/gecko/generated/structs_{debug|release}.rs` are re-generated (they still use the old alias).
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The alias is left there temporarilly and will be removed completely in a later commit where
also components/style/gecko/generated/structs_{debug|release}.rs are re-generated (they still
use the old alias).
