Track UMA stats for when the renderer side audio device wasn't ready.

content/browser/renderer_host/media/audio_sync_reader.h

Index: content/browser/renderer_host/media/audio_sync_reader.h
diff --git a/content/browser/renderer_host/media/audio_sync_reader.h b/content/browser/renderer_host/media/audio_sync_reader.h
index b2c3b1ffcd5cbf97d030dcb6de30b29568ec73bb..1f07b200b0cf3904c63b5b217e0007eff81a0689 100644
--- a/content/browser/renderer_host/media/audio_sync_reader.h
+++ b/content/browser/renderer_host/media/audio_sync_reader.h
@@ -67,6 +67,11 @@ class AudioSyncReader : public media::AudioOutputController::SyncReader {
   // Maximum amount of audio data which can be transferred in one Read() call.
   int packet_size_;
 
+  // Track the number of times the renderer missed its real-time deadline and
+  // report a UMA stat during destruction.
+  size_t renderer_callback_count_;
+  size_t renderer_missed_callback_count_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioSyncReader);
 };