Specifically, consider adding checks to VRDisplayImpl::GetPose() and VRDisplayImpl::GetFrameData().

If we wanted to add focus checks for presentation/exclusive sessions, we'd to add those in the implementations of VRPresentationProvider::GetVSync().

We should also consider sending blur/focus events on the session when the page loses/gains focus.

This would allow developers that care when rendering/access to the device is 'paused' to implement that in a consistent way instead of having to listen to both window blur and device blur.

There's also the question of do we send device blur/focus events to the session when it doesn't have frame focus. We currently would, which would potentially allow backgrounded pages to record things like when the user takes their headset off. (This problem goes away if we blur when losing frame focus, as we won't re-blur if the headset is taken off or something)

Removing Blink>WebVR component and assigning to Blink>WebXR 

Removing Blink>WebVR component and assigning to Blink>WebXR 

Added estimate 10d:
mthiessen@ says 5d engineering effort (3 impl + 2 test)
lincolnfrog@ estimates 5d spec work - write design doc, file issue, gather feedback, etc. Not calendar days but total days of work to figure out spec.

Relevant spec issue: https://github.com/immersive-web/privacy-and-security/issues/9. This should result in a change to WebXR Device API that we would implement.