Refactor the TrayAudio code so that it can be used by other platforms.

chromeos/audio/cras_audio_handler.cc

 // Copyright (c) 2013 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 "chromeos/audio/cras_audio_handler.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/bind.h"
@@ skipping 112 matching lines @@
   return input_mute_on_;
 }
 
 bool CrasAudioHandler::IsInputMutedForDevice(uint64 device_id) {
   const AudioDevice* device = GetDeviceFromId(device_id);
   if (!device)
     return false;
   return audio_pref_handler_->GetMuteValue(*device);
 }
 
+int CrasAudioHandler::GetOutputDefaultVolumeMuteThreshold() {
+  return kMuteThresholdPercent;
+}
+
 int CrasAudioHandler::GetOutputVolumePercent() {
   return output_volume_;
 }
 
 int CrasAudioHandler::GetOutputVolumePercentForDevice(uint64 device_id) {
   if (device_id == active_output_node_id_) {
     return output_volume_;
   } else {
     const AudioDevice* device = GetDeviceFromId(device_id);
     return static_cast<int>(audio_pref_handler_->GetOutputVolumeValue(device));
@@ skipping 546 matching lines @@
   UpdateDevicesAndSwitchActive(node_list);
   FOR_EACH_OBSERVER(AudioObserver, observers_, OnAudioNodesChanged());
 }
 
 void CrasAudioHandler::HandleGetNodesError(const std::string& error_name,
                                            const std::string& error_msg) {
   LOG_IF(ERROR, log_errors_) << "Failed to call GetNodes: "
       << error_name  << ": " << error_msg;
 }
 }  // namespace chromeos