GitLab

Adds an audio focus flag that enables audio focus manager but
disables enforcement of a single media session. This gives us
the option of enabling audio focus tracking without the user
facing change of enforcing a single media session.

BUG=875004

Change-Id: I5415ec76db7b22d4d91ea98c92e3f1515d9df97b
Reviewed-on: https://chromium-review.googlesource.com/c/1231915
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596446}