Add UMA histograms for time spent getting WebRTC audio render data.

content/renderer/media/webrtc_audio_renderer.h

Index: content/renderer/media/webrtc_audio_renderer.h
diff --git a/content/renderer/media/webrtc_audio_renderer.h b/content/renderer/media/webrtc_audio_renderer.h
index f4f677ee58f58e34b0918217ceae891ee3b8da92..2808670bd958d139d0535638f3f35ca2e3a8f77d 100644
--- a/content/renderer/media/webrtc_audio_renderer.h
+++ b/content/renderer/media/webrtc_audio_renderer.h
@@ -250,10 +250,17 @@ class CONTENT_EXPORT WebRtcAudioRenderer
   // before being destructed (PlayingState object goes out of scope).
   SourcePlayingStates source_playing_states_;
 
-  // Used for triggering new UMA histogram. Counts number of render
-  // callbacks modulo |kNumCallbacksBetweenRenderTimeHistograms|.
+  // Used for logging UMA data periodically.
   int render_callback_count_;
 
+  // Accumulated time spent waiting for render data from the source. Used for
+  // logging UMA data for average time spent waiting.
+  base::TimeDelta accumulated_render_time_;
+
+  // Stores the maximum time spent waiting for render data from the source. Used
+  // for logging UMA data. Logged and reset when Stop() is called.
+  base::TimeDelta max_render_time_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebRtcAudioRenderer);
 };