GitLab

For cross process audio focus requests we need to support
async audio focus requests in MediaSessionImpl. This adds
support and test coverage but does not yet fully convert
them to async.

BUG=875004

Change-Id: Ie4236b5e78d63593d9ec3bf0968e03bef36ee1fc
Reviewed-on: https://chromium-review.googlesource.com/c/1192105
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596371}