Support audio output device enumeration and selection in PPAPI

content/renderer/pepper/pepper_audio_controller.h

 // Copyright 2016 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 CONTENT_RENDERER_PEPPER_PEPPER_AUDIO_CONTROLLER_H_
 #define CONTENT_RENDERER_PEPPER_PEPPER_AUDIO_CONTROLLER_H_
 
 #include <set>
 
 #include "base/macros.h"
 
 namespace content {
 
+class PepperAudioOutputHost;
 class PepperPluginInstanceImpl;
 class PPB_Audio_Impl;
 
 /**
  * This class controls all the active audio instances of a Pepper instance.
  * This class can only be a non-shareable member of PepperPluginInstanceImpl.
  */
 class PepperAudioController {
  public:
   explicit PepperAudioController(PepperPluginInstanceImpl* instance);
   virtual ~PepperAudioController();
 
   // Adds an audio instance to the controller.
   void AddInstance(PPB_Audio_Impl* audio);
+  void AddInstance(PepperAudioOutputHost* audio_output);
 
   // Removes an audio instance from the controller.
   void RemoveInstance(PPB_Audio_Impl* audio);
+  void RemoveInstance(PepperAudioOutputHost* audio_output);
 
   // Sets the volume of all audio instances.
   void SetVolume(double volume);
 
   // The pepper instance has been deleted. This method can only be called
   // once. The controller will be invalidated after this call, and then all
   // other methods will be no-op.
   void OnPepperInstanceDeleted();
 
  private:
   // Notifies the RenderFrame that the playback has stopped.  This method should
   // only be called when |ppb_audios_| turns from non-empty to empty.
   void NotifyPlaybackStopsOnEmpty();
 
-  // All active audio instances.
+  // Helper functions to deal with the first and last audio instance.
+  void StartPlaybackIfFirstInstance();
+  void StopPlaybackIfLastInstance();
+
+  // All active audio instances that are using the old
+  // PPB_Audio interface.
   std::set<PPB_Audio_Impl*> ppb_audios_;
 
+  // All active audio output instances that are using the new
+  // PPB_AudioOutput interface.
+  std::set<PepperAudioOutputHost*> audio_output_hosts_;
+
   // The Pepper instance which this controller is for. Will be null after
   // OnPepperInstanceDeleted() is called.
   PepperPluginInstanceImpl* instance_;
 
   DISALLOW_COPY_AND_ASSIGN(PepperAudioController);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_AUDIO_CONTROLLER_H_