Prevent media::ClocklessAudioSink from stopping already stopped threads.

media/audio/clockless_audio_sink.cc

 // 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.
 
 #include "media/audio/clockless_audio_sink.h"
 
 #include "base/threading/simple_thread.h"
 #include "base/time/time.h"
 #include "media/base/audio_renderer_sink.h"
 
@@ skipping 55 matching lines @@
 ClocklessAudioSink::~ClocklessAudioSink() {}
 
 void ClocklessAudioSink::Initialize(const AudioParameters& params,
                                     RenderCallback* callback) {
   DCHECK(!initialized_);
   thread_.reset(new ClocklessAudioSinkThread(params, callback));
   initialized_ = true;
 }
 
 void ClocklessAudioSink::Start() {
+  DCHECK(initialized_);
   DCHECK(!playing_);
 }
 
 void ClocklessAudioSink::Stop() {
-  DCHECK(initialized_);
-
-  if (!playing_)
-    return;
-
-  playback_time_ = thread_->Stop();
+  Pause();
 }
 
 void ClocklessAudioSink::Play() {
   DCHECK(initialized_);
 
   if (playing_)
     return;
 
   playing_ = true;
   thread_->Start();
 }
 
 void ClocklessAudioSink::Pause() {
-  Stop();
+  DCHECK(initialized_);
+
+  if (!playing_)
+    return;
+
+  playing_ = false;
+  playback_time_ = thread_->Stop();
 }
 
 bool ClocklessAudioSink::SetVolume(double volume) {
   // Audio is always muted.
   return volume == 0.0;
 }
 
 }  // namespace media