Currently, there is a delay before WebVR content or the VR UI are shown after the DON flow. This is at least partially due to the time it takes to start the VR UI.

We should investigate mitigations, including:
1. Deferring VR UI startup.
 * For most WebVR content (HTTPS), this is not needed initially.
 * We still need to start it up soon after entering VR so we can be responsive to menu mode.
 * This is not an option for VR browsing.
2. Parallelize startup with the Daydream DON flow.
 * This assumes our process(es) are not suspended during this time.
 * Even so, it is possible there are would be some gain in reordering things.