Enable audio volume control on Android.

media/audio/android/audio_manager_android.cc

 // 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.
 
 #include "media/audio/android/audio_manager_android.h"
 
 #include "base/logging.h"
 #include "jni/AudioManagerAndroid_jni.h"
 #include "media/audio/android/opensles_input.h"
 #include "media/audio/android/opensles_output.h"
@@ skipping 54 matching lines @@
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
       GetNativeOutputSampleRate(), 16,
       buffer_size <= 0 ? kDefaultInputBufferSize : buffer_size);
 }
 
 AudioOutputStream* AudioManagerAndroid::MakeAudioOutputStream(
     const AudioParameters& params, const std::string& input_device_id) {
   AudioOutputStream* stream =
     AudioManagerBase::MakeAudioOutputStream(params, std::string());
-  if (stream && output_stream_count() == 1)
+  if (stream && output_stream_count() == 1) {
+    SetAudioMode(kAudioModeInCommunication);
     RegisterHeadsetReceiver();
+  }
   return stream;
 }
 
 AudioInputStream* AudioManagerAndroid::MakeAudioInputStream(
     const AudioParameters& params, const std::string& device_id) {
   AudioInputStream* stream =
     AudioManagerBase::MakeAudioInputStream(params, device_id);
-  if (stream && input_stream_count() == 1)
-    SetAudioMode(kAudioModeInCommunication);
   return stream;
 }
 
 void AudioManagerAndroid::ReleaseOutputStream(AudioOutputStream* stream) {
   AudioManagerBase::ReleaseOutputStream(stream);
-  if (!output_stream_count())
+  if (!output_stream_count()) {
     UnregisterHeadsetReceiver();
+    SetAudioMode(kAudioModeNormal);
+  }
 }
 
 void AudioManagerAndroid::ReleaseInputStream(AudioInputStream* stream) {
   AudioManagerBase::ReleaseInputStream(stream);
-  if (!input_stream_count())
-    SetAudioMode(kAudioModeNormal);
 }
 
 AudioOutputStream* AudioManagerAndroid::MakeLinearOutputStream(
       const AudioParameters& params) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LINEAR, params.format());
   return new OpenSLESOutputStream(this, params);
 }
 
 AudioOutputStream* AudioManagerAndroid::MakeLowLatencyOutputStream(
       const AudioParameters& params, const std::string& input_device_id) {
@@ skipping 85 matching lines @@
       j_audio_manager_.obj());
 }
 
 int AudioManagerAndroid::GetAudioLowLatencyOutputFrameSize() {
   return Java_AudioManagerAndroid_getAudioLowLatencyOutputFrameSize(
       base::android::AttachCurrentThread(),
       j_audio_manager_.obj());
 }
 
 }  // namespace media