Enhance Visualizer behavior in the case of mediaserver death.

Bring the Visualizer class into line with the SDK documentation by
returning ERROR_DEAD_OBJECT instead of ERROR_INVALID_OPERATION when
the Visualizer loses its binder connection to the mediaserver because
of a mediaserver restart.

Also add a new callback interface to allow clients to be
asynchronously notified in the case of server death.  Right now, the
interface definition and the registration method are flagged as hidden
pending API council review/approval.

See http://b/issue?id=5717519

 for details.

Change-Id: Ic15856f27ed5a950a583ac11ca81f79bd7e9b1a0
Signed-off-by: John Grossman <johngro@google.com>