Mute audio when volume is zero on Android.

media/audio/android/opensles_output.cc

Index: media/audio/android/opensles_output.cc
diff --git a/media/audio/android/opensles_output.cc b/media/audio/android/opensles_output.cc
index 5643f833c3dd98f53eeb578e13e6ff4aaf9c6887..77e6778dbcf618dae106561239b7b9c563fd73f8 100644
--- a/media/audio/android/opensles_output.cc
+++ b/media/audio/android/opensles_output.cc
@@ -28,6 +28,7 @@ OpenSLESOutputStream::OpenSLESOutputStream(AudioManagerAndroid* manager,
       active_buffer_index_(0),
       buffer_size_bytes_(0),
       started_(false),
+      muted_(false),
       volume_(1.0) {
   DVLOG(2) << "OpenSLESOutputStream::OpenSLESOutputStream()";
   format_.formatType = SL_DATAFORMAT_PCM;
@@ -172,6 +173,12 @@ void OpenSLESOutputStream::GetVolume(double* volume) {
   *volume = static_cast<double>(volume_);
 }
 
+void OpenSLESOutputStream::SetMute(bool muted) {
+  DVLOG(2) << "OpenSLESOutputStream::SetMute(" << muted << ")";
+  DCHECK(thread_checker_.CalledOnValidThread());
+  muted_ = muted;
+}
+
 bool OpenSLESOutputStream::CreatePlayer() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!engine_object_.Get());
@@ -324,7 +331,7 @@ void OpenSLESOutputStream::FillBufferQueueNoLock() {
   // Note: If the internal representation ever changes from 16-bit PCM to
   // raw float, the data must be clipped and sanitized since it may come
   // from an untrusted source such as NaCl.
-  audio_bus_->Scale(volume_);
+  audio_bus_->Scale(muted_ ? 0.0f : volume_);
   audio_bus_->ToInterleaved(frames_filled,
                             format_.bitsPerSample / 8,
                             audio_data_[active_buffer_index_]);