WebContentsAudioMuter: Mute all audio output from a WebContentsImpl.

content/browser/media/capture/web_contents_audio_muter.h

Index: content/browser/media/capture/web_contents_audio_muter.h
diff --git a/content/browser/media/capture/web_contents_audio_muter.h b/content/browser/media/capture/web_contents_audio_muter.h
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+// 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_CAPTURE_WEB_CONTENTS_AUDIO_MUTER_H_
+#define CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_AUDIO_MUTER_H_
+
+#include "base/memory/ref_counted.h"
+
+namespace content {
+
+class WebContents;
+
+// Mutes all audio output from a WebContents.  Internally, this is accomplished
+// by providing a MirroringDestination implementation, similar to that found in
+// WebContentsAudioInputStream for audio capture/mirroring.  However, the
+// WebContentsAudioMuter::MuteDestination only pumps the audio data and discards
+// it.
+class WebContentsAudioMuter {
+ public:
+  explicit WebContentsAudioMuter(WebContents* web_contents);
+  ~WebContentsAudioMuter();
+
+  bool is_muting() const { return is_muting_; }
+
+  void StartMuting();
+  void StopMuting();
+
+ private:
+  // AudioMirroringManager::MirroringDestination implementation which is
+  // ref-counted so it remains alive as tasks referencing it are posted on both
+  // the UI and IO threads.
+  class MuteDestination;
+  const scoped_refptr<MuteDestination> destination_;
+
+  bool is_muting_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebContentsAudioMuter);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_AUDIO_MUTER_H_