GitLab

The SmoothnessHelper now measures how many consecutive windows have
a proportion of dropped frames that's over a threshold.  It outputs
a training example with maximum such number found over a playback.

Additionally, it now assumes that it will be created when playback
starts, and will be destroyed when it ends, rather than taking an
explicit "is playing" signal.  If the feature vector changes, then
the SmoothnessHelper should be destroyed / reconstructed too.

Change-Id: I8ceef55f33d6d8164f4a6e2d0e1c77fdbbce53e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2004071
Commit-Queue: Frank Liberato <liberato@chromium.org>
Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732673}