Create abstract interface for media::Pipeline.

content/renderer/media/render_media_log.h

 // Copyright (c) 2012 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 CONTENT_RENDERER_MEDIA_RENDER_MEDIA_LOG_H_
 #define CONTENT_RENDERER_MEDIA_RENDER_MEDIA_LOG_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
 #include "media/base/media_log.h"
 
+namespace base {
+class TickClock;
+}
+
 namespace content {
 
 // RenderMediaLog is an implementation of MediaLog that forwards events to the
 // browser process, throttling as necessary.
 //
 // To minimize the number of events sent over the wire, only the latest event
 // added is sent for high frequency events (e.g., BUFFERED_EXTENTS_CHANGED).
 //
 // It must be constructed on the render thread.
 class CONTENT_EXPORT RenderMediaLog : public media::MediaLog {
@@ skipping 24 matching lines @@
 
   // Limits the number buffered extents changed events we send over IPC to one.
   scoped_ptr<media::MediaLogEvent> last_buffered_extents_changed_event_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderMediaLog);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_RENDER_MEDIA_LOG_H_