audio flinger: do not call JAVA services until system is ready

Wait for system ready indication form AudioService before enabling
calls to scheduling service or power manager.

Bug: 11520969.
Change-Id: I221927394f4a08fd86c9d457e55dd0e07949f0cf
diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index 3241e9c..26cffa6 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -158,6 +158,9 @@
     // or no HW sync source is used.
     static audio_hw_sync_t getAudioHwSyncForSession(audio_session_t sessionId);
 
+    // Indicate JAVA services are ready (scheduling, power management ...)
+    static status_t systemReady();
+
     // Events used to synchronize actions between audio sessions.
     // For instance SYNC_EVENT_PRESENTATION_COMPLETE can be used to delay recording start until
     // playback is complete on another audio session.