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/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 4c2e77b..6c2c226 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -423,6 +423,13 @@
     return af->getAudioHwSyncForSession(sessionId);
 }
 
+status_t AudioSystem::systemReady()
+{
+    const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
+    if (af == 0) return NO_INIT;
+    return af->systemReady();
+}
+
 // ---------------------------------------------------------------------------