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This PR implements the plumbing for paint worklets:
* Adding CSS values for paint worklets.
* Implementing a skeleton for the `PaintWorkletGlobalScope` webidl.
* Implementing an executor for paint worklet tasks, and passing it from script to layout.
* Building the display list items for paint worklet images.
This PR does not implement registering or calling paint worklets in JS.
Before it merges, this PR needs a reftest added for basic paint worklet functionality.
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<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] There are tests for these changes
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Source-Repo: https://github.com/servo/servo
Source-Revision: bf46da065db58549a74c489d521f9375f4137637
Adapted from #15887.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#15409
- [X] There are tests for these changes
Source-Repo: https://github.com/servo/servo
Source-Revision: 62690887c163332688add2b1e62bb4c12b2e7df4
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#15701.
- [X] These changes do not require new tests because there should already be WPTs for image loads.
Source-Repo: https://github.com/servo/servo
Source-Revision: c85a02b14431ce775024d8a8dae9d3e727dedfc4
