Add a sampling profiler
This uses the code already built for the background hang monitor and adds the ability to repeatedly sample all monitored threads. This sampling allows us to generate profiles that we can translate into the format used by https://perf-html.io/, allowing us to benefit from modern Gecko performance tooling.
You can run Servo with `PROFILE_OUTPUT=foo.json` and `SAMPLING_RATE=50` (for example), otherwise these values will default to `samples.json` and 10ms, respectively. To activate the profiler, press cmd+p, and to stop profiling, press cmd+p again. This will the captured samples to be symbolicated, which will take a very long time, and eventually there will be a new JSON profile in the output location.
To create a profile for use by Gecko's tools, run `python etc/profilicate.py path/to/profile.json >gecko_profile.json`, and load `gecko_profile.json` in the https://perf-html.io/ to see something like [this](https://profiler.firefox.com/public/8137e2b11fbb92afb80090bc534fd83015c87ee6/calltree/?globalTrackOrder=0-1&thread=1&v=3);
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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#13103
- [x] These changes do not require tests because way too many pieces to automate
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Use a test VRDisplay that renders to a GL window
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Add a `dom.webvr.test` pref that registers a new VR display, which registers to a GL window.
The matching webvr PR is https://github.com/servo/rust-webvr/pull/66.
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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#22795
- [X] These changes do not require tests because we need a followup PR to support reftests which use the VR display
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Use simpleservo embedding API for Magic Leap
This removes the duplication between the two ports and makes it easier to improve all of our embeddings simultaneously.
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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#22065
- [x] These changes do not require tests because no automated tests for embedded devices.
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Support for ExternalVR implementation
This PR adds the hook necessary for the ExternalVR rust-webvr driver.
Waiting on rust-webvr 0.9.3 to be published before landing.
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