Media Session API: use MediaMetadata in the browser process.
This is adding a Java counterpart to the content::MediaMetadata added in Java
with a proxy to pass the object from C++ to Java.
The MediaMetadata information are only used to replace the title from the media
notification and set some Android metadata. Other UI changes will require UI
review.
BUG=497735,581728
Review URL: https://codereview.chromium.org/1458703003
Cr-Commit-Position: refs/heads/master@{#381697}
20 files changed
