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

media/renderers/audio_renderer_impl.cc

Index: media/renderers/audio_renderer_impl.cc
diff --git a/media/renderers/audio_renderer_impl.cc b/media/renderers/audio_renderer_impl.cc
index 4899be0a4b98470bf59c19947695bf431bb11610..53d9cceb4a47e73524111edbf5ca8ec0235a6ad3 100644
--- a/media/renderers/audio_renderer_impl.cc
+++ b/media/renderers/audio_renderer_impl.cc
@@ -58,6 +58,7 @@ AudioRendererImpl::AudioRendererImpl(
       received_end_of_stream_(false),
       rendered_end_of_stream_(false),
       is_suspending_(false),
+      rendered_first_frame_(false),
       weak_factory_(this) {
   audio_buffer_stream_->set_config_change_observer(base::Bind(
       &AudioRendererImpl::OnConfigChange, weak_factory_.GetWeakPtr()));
@@ -173,6 +174,7 @@ void AudioRendererImpl::SetMediaTime(base::TimeDelta time) {
   ended_timestamp_ = kInfiniteDuration;
   last_render_time_ = stop_rendering_time_ = base::TimeTicks();
   first_packet_timestamp_ = kNoTimestamp;
+  rendered_first_frame_ = false;
   audio_clock_.reset(new AudioClock(time, audio_parameters_.sample_rate()));
 }
 
@@ -767,6 +769,10 @@ int AudioRendererImpl::Render(base::TimeDelta delay,
   {
     base::AutoLock auto_lock(lock_);
     last_render_time_ = tick_clock_->NowTicks();
+    if (!rendered_first_frame_) {
+      rendered_first_frame_ = true;
+      client_->OnFirstFrameRender();
+    }
 
     int64_t frames_delayed = AudioTimestampHelper::TimeToFrames(
         delay, audio_parameters_.sample_rate());