GitLab

AddVSyncCompleteCallback is meant to be called from inside BeginFrame
and to be called immediately after all observers have been notified.
* Make sure all BeginFrame calls are followed by Complete callbacks, not
  just ones from VSync.
* Rename it to AddBeginFrameCompletionCallback to clarify this.
* Release CHECK that AddVSyncCompleteCallback is only called from with
  BeginFrame

Bug: 885124
Change-Id: Ib2c5c8e7870a4876da2d3d2742ed396e3e87d941
Reviewed-on: https://chromium-review.googlesource.com/c/1315970
Commit-Queue: Bo <boliu@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605084}