Assign blame for playback wakelocks.

Set a work source for the playback wakelock, so that playback is
counted against the requesting app instead of the media server.

Cherrypicked from master.

b/9464621

Change-Id: I7329f88a288a95a582a78005a1c3d16a5a611e31
diff --git a/media/libmediaplayerservice/MediaPlayerService.h b/media/libmediaplayerservice/MediaPlayerService.h
index 21f4117..05d44d4 100644
--- a/media/libmediaplayerservice/MediaPlayerService.h
+++ b/media/libmediaplayerservice/MediaPlayerService.h
@@ -72,7 +72,7 @@
         class CallbackData;
 
      public:
-                                AudioOutput(int sessionId);
+                                AudioOutput(int sessionId, int uid);
         virtual                 ~AudioOutput();
 
         virtual bool            ready() const { return mTrack != 0; }
@@ -135,6 +135,7 @@
         uint32_t                mSampleRateHz; // sample rate of the content, as set in open()
         float                   mMsecsPerFrame;
         int                     mSessionId;
+        int                     mUid;
         float                   mSendLevel;
         int                     mAuxEffectId;
         static bool             mIsOnEmulator;