Added a callback in nuplayer via informational event to signal the start of video rendering

Change-Id: Id7b9b82d4e5467ad8701bfbad4dcc5070f3703cf
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
index 268628b..e4368c7 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
@@ -45,9 +45,10 @@
     void resume();
 
     enum {
-        kWhatEOS                = 'eos ',
-        kWhatFlushComplete      = 'fluC',
-        kWhatPosition           = 'posi',
+        kWhatEOS                 = 'eos ',
+        kWhatFlushComplete       = 'fluC',
+        kWhatPosition            = 'posi',
+        kWhatVideoRenderingStart = 'vdrd',
     };
 
 protected:
@@ -99,6 +100,7 @@
     bool mSyncQueues;
 
     bool mPaused;
+    bool mVideoRenderingStarted;
 
     int64_t mLastPositionUpdateUs;
     int64_t mVideoLateByUs;
@@ -120,6 +122,7 @@
     void notifyFlushComplete(bool audio);
     void notifyPosition();
     void notifyVideoLateBy(int64_t lateByUs);
+    void notifyVideoRenderingStart();
 
     void flushQueue(List<QueueEntry> *queue);
     bool dropBufferWhileFlushing(bool audio, const sp<AMessage> &msg);