[ui/vr] Notify tab ui about VR state change

Bug: 845252
Change-Id: I6a2788cd612eba36482a1b2a0594d621c485ee5b
Reviewed-on: https://chromium-review.googlesource.com/c/1412952
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Bill Orr <billorr@chromium.org>
Commit-Queue: Suman Kancherla <sumankancherla@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623527}
3 files changed