cras_audio_handler add SetOutputMono method

chromeos/audio/cras_audio_handler.h

 // 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.
 
 #ifndef CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 #define CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 #include <queue>
@@ skipping 48 matching lines @@
 
     // Called when audio nodes changed.
     virtual void OnAudioNodesChanged();
 
     // Called when active audio node changed.
     virtual void OnActiveOutputNodeChanged();
 
     // Called when active audio input node changed.
     virtual void OnActiveInputNodeChanged();
 
+    // Called when output channel remixing changed.
+    virtual void OnOuputChannelRemixingChanged(bool mono_on);
+
    protected:
     AudioObserver();
     virtual ~AudioObserver();
     DISALLOW_COPY_AND_ASSIGN(AudioObserver);
   };
 
   enum DeviceActivateType {
     ACTIVATE_BY_PRIORITY = 0,
     ACTIVATE_BY_USER,
     ACTIVATE_BY_RESTORE_PREVIOUS_STATE,
@@ skipping 120 matching lines @@
   // remain active. Otherwise, the old active nodes will be de-activated before
   // we activate the new nodes with the same type(input/output).
   virtual void ChangeActiveNodes(const NodeIdList& new_active_ids);
 
   // Swaps the left and right channel of the internal speaker.
   // Swap the left and right channel if |swap| is true; otherwise, swap the left
   // and right channel back to the normal mode.
   // If the feature is not supported on the device, nothing happens.
   virtual void SwapInternalSpeakerLeftRightChannel(bool swap);
 
+  // Accessibility audio setting: sets the output mono or not.
+  virtual void SetOutputMono(bool mono_on);
+
+  // Returns true if output mono is enabled.
+  virtual bool IsOutputMonoEnabled() const;
+
   // Enables error logging.
   virtual void LogErrors();
 
   // If necessary, sets the starting point for re-discovering the active HDMI
   // output device caused by device entering/exiting docking mode, HDMI display
   // changing resolution, or chromeos device suspend/resume. If
   // |force_rediscovering| is true, it will force to set the starting point for
   // re-discovering the active HDMI output device again if it has been in the
   // middle of rediscovering the HDMI active output device.
   virtual void SetActiveHDMIOutoutRediscoveringIfNecessary(
@@ skipping 182 matching lines @@
   bool input_mute_on_;
   int output_volume_;
   int input_gain_;
   uint64_t active_output_node_id_;
   uint64_t active_input_node_id_;
   bool has_alternative_input_;
   bool has_alternative_output_;
 
   bool output_mute_locked_;
 
+  // Audio output channel counts.
+  int32_t channels_;

[jennyz, 2016/03/30 23:39:26]

How about naming it output_channels_? 

+  bool output_mono_on_;
+
   // Failures are not logged at startup, since CRAS may not be running yet.
   bool log_errors_;
 
   // Timer for HDMI re-discovering grace period.
   base::OneShotTimer hdmi_rediscover_timer_;
   int hdmi_rediscover_grace_period_duration_in_ms_;
   bool hdmi_rediscovering_;
 
   bool cras_service_available_ = false;
 
   base::WeakPtrFactory<CrasAudioHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CrasAudioHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_