Preliminary WebXR support
This implements just enough WebXR to display to 3DOF devices in
immersive mode only.
Couple missing things:
- [ ] Handling reference spaces (even if just supporting eye-level spaces)
- [x] Spec links
- [ ] We enter immersive mode when baseLayer is set, but it seems like
we're supposed to do this when requestSession is called (https://github.com/immersive-web/webxr/issues/453)
- [ ] VR/XR should block less (https://github.com/servo/servo/issues/22505)
- [x] More pref-gating
- [x] `views` is a method instead of an attribute because we don't support FrozenArray
<s>Once I add spec links and pref gating</s> this can be landed as-is for further experimentation.
r? @jdm @MortimerGoro
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Serialize the children of void html elements as empty strings
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Fix certifi import error while running ./match bootstrap
Fixes#22590
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Add missing build dependencies for openSUSE
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GStreamer development packages and Autotools 2.13 are required for a successful build of servo on openSUSE Linux.
This commit adds missing dependencies (compare with e.g. Fedora and Arch).
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