GL context loss can happen when we're rendering to a surface (as opposed to surface-less rendering) if we lose visibility.

We render to a surface in two cases: Pre-Daydream devices, and when we fail to turn on Asynchronous Reprojection on Daydream devices (I'm not aware of a situation where this could happen).

Supporting re-creating our GL context is hard, so for Pre-Daydream devices we should just exit VR when we lose our context - this isn't a huge issue for Cardboard users and should happen extremely rarely (we don't expect to lose visibility during XR presentation.

For Daydream devices, we should just not enter VR if we can't turn on Async Reprojection for two reasons:
1. The experience will suck.
2. Going to dashboard and back will crash Chrome as our GL context will be lost.