GitLab

After no streams have been playing out audio for a few seconds, trigger
power-save mode. Note that paused streams do not count as playing out
for this purpose.

Bug: internal b/64462358
Change-Id: I6ed4910490705d39e499b5f5e63432f8534993ff
Reviewed-on: https://chromium-review.googlesource.com/807749
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522030}