PlaybackStateCompat: Add support for custom actions, extras, and active item id

Adds support for API 21 and 22 specific PlaybackState data, allowing developers to use custom actions, active queue item ids, and extras while maintaining backward compatibility.

These newly added elements are not part of the RemoteControlClient API surface and are ignored on older devices.

BUG: 19382699
Change-Id: Idf355f6414a1035b2ae50bc3612a0deda81e4460
4 files changed