Add metrics for tracking underflow during src= playback.

media/blink/webmediaplayer_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_
 #define MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/cancelable_callback.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread.h"
+#include "base/timer/elapsed_timer.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "media/base/media_tracks.h"
 #include "media/base/pipeline_impl.h"
 #include "media/base/renderer_factory.h"
 #include "media/base/surface_manager.h"
 #include "media/base/text_track.h"
 #include "media/blink/buffered_data_source_host_impl.h"
 #include "media/blink/media_blink_export.h"
 #include "media/blink/multibuffer_data_source.h"
@@ skipping 503 matching lines @@
   CanSuspendState can_suspend_state_;
 
   // Called some-time after OnHidden() if the media was suspended in a playing
   // state as part of the call to OnHidden().
   base::OneShotTimer background_pause_timer_;
 
   // Monitors the watch time of the played content.
   std::unique_ptr<WatchTimeReporter> watch_time_reporter_;
   bool is_encrypted_;
 
+  // Number of times we've reached BUFFERING_HAVE_NOTHING during playback.
+  int underflow_count_;
+  std::unique_ptr<base::ElapsedTimer> underflow_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBMEDIAPLAYER_IMPL_H_