Correctly handle enumerations for AudioManagers that report only the default audio output device.

content/browser/renderer_host/media/audio_output_device_enumerator.h

 // Copyright (c) 2015 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.
 
 // AudioOutputDeviceEnumerator is used to enumerate audio output devices.
 // It can return cached results of previous enumerations in order to boost
 // performance.
 // All its public methods must be called on the thread where the object is
 // created.
 
@@ skipping 25 matching lines @@
 
 // AudioOutputDeviceInfo describes information about an audio output device.
 // The enumerations returned by AudioOutputDeviceEnumerator::Enumerate() contain
 // elements of this type. It is used only in the browser side.
 struct AudioOutputDeviceInfo {
   std::string unique_id;
   std::string device_name;
   media::AudioParameters output_params;
 };
 
-typedef std::vector<AudioOutputDeviceInfo> AudioOutputDeviceEnumeration;
+struct AudioOutputDeviceEnumeration {
+ public:
+  AudioOutputDeviceEnumeration(
+      const std::vector<AudioOutputDeviceInfo>& devices,
+      bool has_actual_devices);
+  AudioOutputDeviceEnumeration();
+  ~AudioOutputDeviceEnumeration();
+
+  std::vector<AudioOutputDeviceInfo> devices;
+  bool has_actual_devices;
+};
+
 typedef base::Callback<void(const AudioOutputDeviceEnumeration&)>
     AudioOutputDeviceEnumerationCB;
 
 class CONTENT_EXPORT AudioOutputDeviceEnumerator {
  public:
   enum CachePolicy {
     CACHE_POLICY_NO_CACHING,
     CACHE_POLICY_MANUAL_INVALIDATION
   };
   AudioOutputDeviceEnumerator(media::AudioManager* audio_manager,
@@ skipping 41 matching lines @@
 
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<AudioOutputDeviceEnumerator> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDeviceEnumerator);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_DEVICE_ENUMERATOR_H_