We should record the number of fallbacks and blank frames.
Bug: webrtc:8040
Change-Id: I92e7b7d7b4664fee6d6bd636609e80e532aa4bd4
Reviewed-on: https://chromium-review.googlesource.com/587688
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Zijie He <zijiehe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#19161}