Add WebGL conformance 2.0.0 tests
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This PR includes WebGL conformance 2.0.0 tests. For now I have disabled three folders in the new suite:
- `Conformance`: Tests WebGL 1.0 API like the current 1.0.3 suite we are using, but it includes a lot more tests and many expectations have to be updated. This is better to do in a separate PR because it will require to update github intermittent paths again and maybe detect new intermittents.
- `Conformance2\textures`: It causes a lot of timeouts because of using videos, svgs, and other complicated formats.
- `deqp`: It's a extra GPU testing suite included in the Khronos 2.0.0 suite. Disabled for now because it causes some timeouts.
So in a nutshell, it uses part of the 2.0.0 suite to test webgl 2.0 and keeps using 1.0.3 in order to test WebGL 1.0. It's good enough to enable TDD for the new WebGL 2.0 features
We can create follow-up issues for the next steps:
* deprecate 1.0.3 and use the new 'conformance' folder in 2.0.0 in order to test WebGL 1.0
* Enable `conformance2/textures` and 'deqp' tests once WebGL 2.0 implementation is more advanced or the timeouts are monitored in more detail.
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added time to interactive metrics
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Added time to interactive metrics and refactored metrics/lib
I need to write tests, but wanted to submit the PR for review
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Wait as late as possible to assign ClipIds
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This will allow Servo to create ClipScrollNodes later during display
list construction, which will be necessary once rounded rectangles
are removed from the LocalClip structure. Instead of keeping track
of the ClipId of each ClipScrollNode, we keep track of its index in an
array of ClipScrollNodes. This will allow us to access them without a
hash lookup.
Update concept of node filter algorithm
Implement new [filter](https://dom.spec.whatwg.org/#concept-node-filter) algorithm from specification
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