unhide MediaSyncEvent class and AudioRecord.startRecording() method with synchronization
event allowing to start audio capture upon occurence of a specific event.
So far the only event defined is playback presentation complete but more events and synchronized
playback/capture methods could be defined in the future.
Change-Id: If05fc6cd125dd9afad451727f792a3fd9e916bef
Added the infrastructure to support the synchronization of playback and
capture actions on specific events.
The first requirement for this feature is to synchronize the audio capture
start with the full rendering of a given audio content.
The applications can further be extended to other use cases
(synchronized playback start...) by adding new synchronization events and
new synchronous control methods on player or recorders.
Also added a method to query the audio session from a ToneGenerator.
Change-Id: I4e47f5108c7cbbd3bd334a7fad9b3b6c5ba55d88
