MediaSessionCompat: Add extra binder into Token

We added an extra binder to support newly added methods after API
level 21. However this requires some time to get the extra binder,
so some methods could failed if they are called before getting the
extra binder. By sharing the extra binder via Token, this CL removes
such time delay.

Bug: 31248021
Test: Passed MediaSessionCompatTest and MediaControllerCompatTest
Change-Id: I8bfeb8585d6f43d6aed55f5dda4f894a7c69193f
7 files changed