VR: Notify delegate when UI has finished loading

This allows the tests to be able to submit events only when the UI
is fully loaded.

Bug: 864840, 864161
Change-Id: I41bb0364d3019910fc0b924fd25fe4a9486e6e90
Reviewed-on: https://chromium-review.googlesource.com/1142033
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Aldo Culquicondor <acondor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576207}
5 files changed