Add optional ANGLE support to glutin port
Supporting ANGLE in Servo has two important benefits:
* we can actually run Servo instances on our Windows CI machines, which gives us more confidence that we're not breaking it
* we can continue to use OpenGL on devices like the Hololens, rather than creating platform-specific graphical backends
<!-- Reviewable:start -->
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/22856)
<!-- Reviewable:end -->
Receive streams in WebRTC (and MediaStreamTrack support)
This adds the `ontrack` event handler to webrtc, and all the `MediaStreamTrack` stuff necessary to make it work.
WebRTC has the ability to group media tracks into streams using MSIDs, but I haven't yet figured out how to do this. For now, `ontrack` should work.
This _should_ be complete, but it hasn't yet been tested (hence the WIP)
r? @ferjm or @jdm
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23342)
<!-- Reviewable:end -->
Enable evaluating javascript in the firefox devtools console
This enables one to use the Firefox Devtools console to evaluate things in servo.
Steps:
start servo: ./mach run tests/html/about-mozilla.html -d --devtools 6000
start firefox and go to Tools -> Web Developer -> Connect...
Set the port to connect to as 6000
Try evaluating things in the console.
<img width="901" alt="Screenshot 2019-05-01 at 13 02 37" src="https://user-images.githubusercontent.com/26968615/57015054-0aa0ce80-6c13-11e9-8031-9299f2da5dba.png">
---
<!-- 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
- [ ] These changes fix #___ (GitHub issue number if applicable)
<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23296)
<!-- Reviewable:end -->
Express GC thresholds as percentages
<!-- Please describe your changes on the following line: -->
According to https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/JSAPI_reference/JS_GetGCParameter, the GC thresholds are percentages.
---
<!-- 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
- [X] These changes fix#23076
- [X] These changes do not require tests because we don't test prefs.json
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23340)
<!-- Reviewable:end -->
Changes for Ubuntu/Ubuntu 19.04 in bootstrap.py
Update handling Ubuntu distributions:
1. script correctly returns error when some version is/was not supported (checked with Ubuntu 19.04)
2. for Ubuntu 19.04 Disco Dingo there are correct packages installed
Note: this is my commit to this project, please forgive any mistakes.
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)
<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because are updating bootstrap.py script
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23324)
<!-- Reviewable:end -->
Fix magicleap debugmozjs
<!-- Please describe your changes on the following line: -->
These changes get magicleap servo to compile with `--debugmozjs`.
---
<!-- 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
- [X] These changes fix#23074 and fix#22069
- [X] These changes do not require tests because we're not building debugmozjs servo for magicleap
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23318)
<!-- Reviewable:end -->
Update harfbuzz to 0.3
`hb_font_funcs_set_glyph_h_kerning_func` is gone but I couldn't find any
replacement. Kerning tests are passing and kerning seems fine on my
computer so I guess it's useless now ?
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23283)
<!-- Reviewable:end -->
`hb_font_funcs_set_glyph_h_kerning_func` is gone but I couldn't find any
replacement. Kerning tests are passing and kerning seems fine on my
computer so I guess it's useless now ?
Finish the implementation of the HTMLMediaElement canPlayType method
<!-- Please describe your changes on the following line: -->
---
<!-- 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
- [X] These changes fix#22299
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23229)
<!-- Reviewable:end -->
