The remote control stack in AudioService is responsible for handling
which application receives media button events. When an application
"registers" its media button receiver, it gets placed at the top
of the remote control stack. If the app also has audio focus (is
at top of focus stack), this will also cause the information of
the attached remote control client (RCC) to be displayed on the
lockscreen.
If an app doesn't re-register its button receiver when it wants
to receive the button events, it might have lost its place at the
top of the remote control stack, and would not show up in the
lockscreen anymore.
This change consists in using the playstate reported by the RCC
to change the remote control stack. If an RCC reports a "playing"
state (e.g. playing, fast forwarding), it is safe to assume the
application is actively being used, and should be the one that
receives the transport control buttons. This CL uses the reported
playstate to conditionally move the corresponding stack entry
to the top of the stack.
Bug 7311023
Change-Id: I1505f01664c16e108b22d33e3f47f0056343676e
a578c48e6c