Add a note to indicate PKG_CONFIG_PATH required
I just got the error messages like #23015 again and then I think the root cause should be about
`PKG_CONFIG_PATH`. After following https://github.com/servo/servo/issues/23015#issuecomment-475050175 said, I can build Servo successfully.
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Promise constructor
In this PR, measures are taken that prevent the ```Promise::new``` constructor from being used outside a compartment.
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Add XRFrame.getPose()
I think I've figured out the model of poses, waiting on Nell for confirmation.
Basically, `getViewerPose(p)` is equivalent to `getPose(source=viewerSpace, relative_to=p)`
The eye-level space, for example, is stationary and stuck to the origin. The position-disabled and identity spaces somewhat counterintuitively follow you around (and appear to be stationary from `getViewerPose()` but not `getPose()`.
The incorrect mental model kinda "works" when looking at only `getViewerPose()`, but we need to figure it out for `getPose()`.
Todo (may add to this PR, but probably not)
- implement `XRSession.viewerSpace`
- implement position-disabled
- implement floor-level (hard to test without a 6dof device)
r? @asajeffrey
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Remove compound microtasks
We handled compound microtasks as microtasks so, basically, we only need
to remove the naming of `compound`.
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Add connectEnd attribute to PerformanceResourceTiming interface
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Update XR code to use rigid transforms and new pose/transform stuff from the spec
This updates our XR code to use euclid's new [RigidTransform3D type](https://github.com/servo/euclid/pull/328), which is more efficent and convenient to work with.
It additionally brings us up to speed with the spec:
- `XRViewerPose` was made a subclass of `XRPose` (https://github.com/immersive-web/webxr/pull/496)
- `XRView.viewMatrix` was removed in favor of `XRRigidTransform.inverse.matrix` (https://github.com/immersive-web/webxr/pull/531)
- `XRRigidTransform.inverse` is an attribute (https://github.com/immersive-web/webxr/pull/560)
- `XRRigidTransform` now validates positions in its constructor (https://github.com/immersive-web/webxr/pull/568)
Furthermore, it adds support for `XRRigidTransform.matrix`.
While fixing this I also noticed that our view matrix code was incorrect, we calculated view matrices as `pose.to_column_major_array()`, whereas it *should* be `pose.inverse().to_row_major_array()` (since Euclid uses row vectors, whenever the spec says it wants a column major array we should use `.to_row_major_array()` since all web specs implicitly use column vectors). For 3DOF devices poses are mostly rotations anyway, so the effective transpose behaved _like_ an inversion, but was incorrect.
This PR gets rid of `view.viewMatrix` anyway, however I felt like I should mention this discrepancy, since otherwise the replacement of `view.viewMatrix` with `view.transform.inverse.matrix` doesn't make sense
r? @jdm
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Users are supposed to use `view.transform.inverse.matrix`
The view matrix was incorrect anyway, we had forgotten to invert it, but that was okay since we transposed it by accident (due to euclid's use of the row-vector convention), and for 3DOF devices these transforms are mostly rotations so transposing instead of inverting doesn't lead to visible effects.
Implement srcObject logic for Blob media providers
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