GitLab

If we currently have audio focus we should re-request
audio focus when the web contents is focused. This
means with grouping the media session that was
last focused will be pushed to the top of the stack.

BUG=906285

Change-Id: I9a7a72897c3c7be1186bdfbc4ef87364f7744a20
Reviewed-on: https://chromium-review.googlesource.com/c/1347614
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611497}