Mute audio when volume is zero on Android.

media/audio/android/opensles_output.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 MEDIA_AUDIO_ANDROID_OPENSLES_OUTPUT_H_
 #define MEDIA_AUDIO_ANDROID_OPENSLES_OUTPUT_H_
 
 #include <SLES/OpenSLES.h>
 #include <SLES/OpenSLES_Android.h>
 
@@ skipping 22 matching lines @@
   virtual ~OpenSLESOutputStream();
 
   // Implementation of AudioOutputStream.
   virtual bool Open() OVERRIDE;
   virtual void Close() OVERRIDE;
   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void SetVolume(double volume) OVERRIDE;
   virtual void GetVolume(double* volume) OVERRIDE;
 
+  // Set the value of |muted_|. It does not affect |volume_| which can be
+  // got by calling GetVolume(). See comments for |muted_| below.
+  void SetMute(bool muted);
+
  private:
   bool CreatePlayer();
 
   // Called from OpenSLES specific audio worker thread.
   static void SimpleBufferQueueCallback(
       SLAndroidSimpleBufferQueueItf buffer_queue,
       void* instance);
 
   // Fills up one buffer by asking the registered source for data.
   // Called from OpenSLES specific audio worker thread.
@@ skipping 36 matching lines @@
 
   // Audio buffers that are allocated in the constructor based on
   // info from audio parameters.
   uint8* audio_data_[kMaxNumOfBuffersInQueue];
 
   int active_buffer_index_;
   size_t buffer_size_bytes_;
 
   bool started_;
 
+  // Volume control coming from hardware. It overrides |volume_| when it's
+  // true. Otherwise, use |volume_| for scaling.
+  // This is needed because platform voice volume never goes to zero in
+  // COMMUNICATION mode on Android.
+  bool muted_;
+
   // Volume level from 0 to 1.
   float volume_;
 
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> audio_bus_;
 
   DISALLOW_COPY_AND_ASSIGN(OpenSLESOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_ANDROID_OPENSLES_OUTPUT_H_