Convert -webkit-linear-gradient coordinate system for Stylo
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This patch will fix the -webkit-linear-gradient direction issue in Stylo. I decided to NOT change the behavior of Servo, because according to the webcompat spec the webkit prefixed version should just be an alias of non-prefixed version. But we might want to remove support for old syntax like "-webkit-linear-gradient(top, ...)" (without "to"), because they are not in the spec anymore.
The Gecko layout system use different coordinate systems for prefixed and non-prefixed version, so I did a conversion, but for Servo I keep the modern version only.
Since I believe we should not support old syntax in Servo, so I'm not going to put the test in Servo. I'll submit my test cases to the Gecko wpt test instead.
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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 [Bug 1372821](https://bugzilla.mozilla.org/show_bug.cgi?id=1372821)
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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because test will be submitted to the Gecko side
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We simply implement ToCss for Option<T>, printing nothing if the value is None,
and we then use SequenceWriter to skip writing of separators around empty parts.
A future patch series has some values that should be separated by spaces. This
allows us to re-use the code for serialization, but the types do get a little
clunky. The separator is now indicated with an associated type.
Implemented the plumbing for paint worklets
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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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