[Media Controller] Add support for a bound controller

Adds a MediaControllerManager interface that supports
creating a MediaController that is bound to a single
media session.

BUG=892771

Change-Id: I060d9859c4896ad556fdd43f9cd7c2102720949a
Reviewed-on: https://chromium-review.googlesource.com/c/1363859
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617931}
8 files changed