Break out WebAudio suspension code into new class. Add tests.

content/renderer/media/renderer_webaudiodevice_impl.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_RENDERER_WEBAUDIODEVICE_IMPL_H_
 #define CONTENT_RENDERER_MEDIA_RENDERER_WEBAUDIODEVICE_IMPL_H_
 
 #include <stdint.h>
 
-#include "base/atomic_ref_count.h"
-#include "base/cancelable_callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/threading/thread_checker.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/audio_renderer_sink.h"
 #include "third_party/WebKit/public/platform/WebAudioDevice.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 #include "url/origin.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
-class NullAudioSink;
+class SilentSinkSuspender;
 }
 
 namespace content {
-
 class RendererWebAudioDeviceImpl
     : public blink::WebAudioDevice,
       public media::AudioRendererSink::RenderCallback {
  public:
   RendererWebAudioDeviceImpl(const media::AudioParameters& params,
                              blink::WebAudioDevice::RenderCallback* callback,
                              int session_id,
                              const url::Origin& security_origin);
   ~RendererWebAudioDeviceImpl() override;
 
@@ skipping 15 matching lines @@
   // Weak reference to the callback into WebKit code.
   blink::WebAudioDevice::RenderCallback* const client_callback_;
 
   // To avoid the need for locking, ensure the control methods of the
   // blink::WebAudioDevice implementation are called on the same thread.
   base::ThreadChecker thread_checker_;
 
   // When non-NULL, we are started.  When NULL, we are stopped.
   scoped_refptr<media::AudioRendererSink> sink_;
 
-  // TODO(miu): Remove this temporary instrumentation to root-cause a memory
-  // use-after-free issue. http://crbug.com/619463
-  base::AtomicRefCount sink_is_running_;
-
   // ID to allow browser to select the correct input device for unified IO.
   int session_id_;
 
-  // Timeticks when the silence starts.
-  base::TimeTicks first_silence_time_ ;
-
-  // TaskRunner to post callbacks to the render thread.
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  // A fake audio sink object that consumes data when long period of silence
-  // audio is detected. This object lives on the render thread.
-  scoped_refptr<media::NullAudioSink> null_audio_sink_;
-
-  // Whether audio output is directed to |null_audio_sink_|.
-  bool is_using_null_audio_sink_;
-
-  // First audio buffer after silence finishes. We store this buffer so that
-  // it can be sent to the |output_device_| later after switching from
-  // |null_audio_sink_|.
-  std::unique_ptr<media::AudioBus> first_buffer_after_silence_;
-
-  bool is_first_buffer_after_silence_;
-
-  // A cancelable task that is posted to start the |null_audio_sink_| after a
-  // period of silence. We do this on android to save battery consumption.
-  base::CancelableClosure start_null_audio_sink_callback_;
-
   // Security origin, used to check permissions for |output_device_|.
   url::Origin security_origin_;
 
+  // Used to suspend |sink_| usage when silence has been detected for too long.
+  std::unique_ptr<media::SilentSinkSuspender> webaudio_suspender_;
+
   DISALLOW_COPY_AND_ASSIGN(RendererWebAudioDeviceImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_RENDERER_WEBAUDIODEVICE_IMPL_H_