style: sync changes from mozilla-central
See each individual commit for details. This also cherry-picks #23463 with a few fixes that were needed in Gecko-only code.
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Instead of per-document. This also allows to reuse this thread-pool if needed
for other stuff, like parallel CSS parsing (#22478), and to share more code with
Gecko, which is always nice.
Current pixel density
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- [x] These changes fix a subset of #11416.
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Measure time required before a layout query is serviced by the layout thread
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- [X] extract QueryMsg from ReflowGoal
- [X] introduce QueryMsg timestamp
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- [x] These changes fix#19795 (github issue number if applicable).
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This allows servo to use the ExternalScrollId API from WebRender fixing
some issues related to duplicate scroll root ids.
Fixes#17176.
Fixes#19287.
Fixes#19648.
