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..272eca08857b3fb8d4315e960bb9eff8dfac509c 100644
--- a/content/renderer/media/webrtc_audio_renderer.h
+++ b/content/renderer/media/webrtc_audio_renderer.h
@@ -250,9 +250,9 @@ 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|.
-  int render_callback_count_;
+  // 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);
 };