Add a pref to indicate user intent to enter webxr
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Add a pref to indicate that the user has indicated intent to enter webxr.
---
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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 do not require tests because it's a command-line pref
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Compile external scripts off the main thread
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---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix#26571 (GitHub issue number if applicable)
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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___
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Add stubs for HTMLCanvasElement.captureStream and WebRTC transceiver APIs
These stubs are hidden by default and only exist to allow getting past the relevant code that invokes them on hubs.mozilla.org.
Add a sessionavailable event that allows content to enter an XR session without a user gesture
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This allows servo to implement immersive web apps. https://immersive-web.github.io/webxr/#application-launch
---
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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 do not require tests because I'm not sure we should have a WPT for something this non-standard.
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Add VTTRegion and part of VTTCue DOM interfaces
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Hello! In this PR I implemented the VTTRegion DOM interface and part of VTTCue (#22312). Before continuing I thought it's maybe a good idea to first request a review or even merge what I did up to this point, as I might get stuck on the next part. I have a slight idea of what needs to be done (I assume it's hooking the GStreamer parser somewhere in `GetCueAsHTML()`), but a short outline or some more instructions would help a lot.
I updated test expectations by first running:
```
./mach test-wpt tests/wpt/web-platform-tests/webvtt/api --log-raw servo.log --pref dom.webvtt.enabled=true
```
then
```
./mach update-wpt servo.log
```
Thanks!
---
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- [ ] These changes fix #___ (GitHub issue number if applicable)
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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because ___
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