Change base::TickClock to a ref counted class.

content/browser/media/audio_stream_monitor.h

 // Copyright 2014 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_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
 #define CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
 
 #include <map>
 #include <utility>
 
 #include "base/callback_forward.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/default_tick_clock.h"
+#include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "media/audio/audio_output_controller.h"
 
 namespace base {
 class TickClock;
 }
 
@@ skipping 81 matching lines @@
 
   // Called by |poll_timer_| to sample the power levels from each of the streams
   // playing in the tab.
   void Poll();
 
   // Compares last known indicator state with what it should be, and triggers UI
   // updates through |web_contents_| if needed.  When the indicator is turned
   // on, |off_timer_| is started to re-invoke this method in the future.
   void MaybeToggle();
 
+  void set_clock_for_testing(const scoped_refptr<base::TickClock>& clock) {
+    clock_ = clock;
+  }
+
   // The WebContents instance instance to receive indicator toggle
   // notifications.  This pointer should be valid for the lifetime of
   // AudioStreamMonitor.
   WebContents* const web_contents_;
 
-  // Note: |clock_| is always |&default_tick_clock_|, except during unit
-  // testing.
-  base::DefaultTickClock default_tick_clock_;
-  base::TickClock* const clock_;
+  // Note: |clock_| is always a DefaultTickClock(), except during unit testing.
+  scoped_refptr<base::TickClock> clock_;
 
   // Confirms single-threaded access in debug builds.
   base::ThreadChecker thread_checker_;
 
   // The callbacks to read power levels for each stream.  Only playing (i.e.,
   // not paused) streams will have an entry in this map.
   typedef std::pair<int, int> StreamID;
   typedef std::map<StreamID, ReadPowerAndClipCallback> StreamPollCallbackMap;
   StreamPollCallbackMap poll_callbacks_;
 
@@ skipping 10 matching lines @@
   // Started only when an indicator is toggled on, to turn it off again in the
   // future.
   base::OneShotTimer<AudioStreamMonitor> off_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioStreamMonitor);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_