PlayerProxy: more control options (pan, delayed start),
remove exceptions in method signatures.
Use delayed start on notification playback for better sync
between media apps and notifications
Disabled for now: support for AudioService (through
MediaFocusControl and PlaybackActivityMonitor) to enforce
audio ducking of focus owners losing audio focus with
AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK, and who don't
play audio that has a content labelled as CONTENT_TYPE_SPEECH.
This feature will be enabled when setting a VolumeShaper
on a player works.
Test: play music and play notification
Bug 30258418
Change-Id: I4e4d911645306bbde17f74288f3b61781fe0e3fe
99489ccf74