[Media] Record time it takes to start rendering audio and video

media/renderers/audio_renderer_impl.h

Index: media/renderers/audio_renderer_impl.h
diff --git a/media/renderers/audio_renderer_impl.h b/media/renderers/audio_renderer_impl.h
index f7915d31a607bdc512ac96704a1ddc7085c8d5cf..df55e6c5529c5156bc22e0c59d8b101f644a827b 100644
--- a/media/renderers/audio_renderer_impl.h
+++ b/media/renderers/audio_renderer_impl.h
@@ -294,6 +294,9 @@ class MEDIA_EXPORT AudioRendererImpl
   // suspend/is suspended and when it resumes.
   bool is_suspending_;
 
+  // Indicates if we've rendered the first valid frame after SetMediaTime().
+  bool rendered_first_frame_;
+
   // End variables which must be accessed under |lock_|. ----------------------
 
   // NOTE: Weak pointers must be invalidated before all other member variables.