[Chromoting] Audio playback won't work after switching default playback device

remoting/host/audio_capturer_win.h

Index: remoting/host/audio_capturer_win.h
diff --git a/remoting/host/audio_capturer_win.h b/remoting/host/audio_capturer_win.h
index d53920a43d9284f6b4ebd8f7d8f5f626b568a87e..0019242fc48f2f9646f6260ab617a9a43c0fbf91 100644
--- a/remoting/host/audio_capturer_win.h
+++ b/remoting/host/audio_capturer_win.h
@@ -31,6 +31,30 @@ class AudioCapturerWin : public AudioCapturer {
   bool Start(const PacketCapturedCallback& callback) override;
 
  private:
+  // An IMMNotificationClient implementation to detect the event of default
+  // audio device recently changed. If it indicates a changed happend recently,
+  // we need to recreate all audio components.
+  class MMNotificationClient;
+
+  // Executes Deinitialize() and Initialize(). If Initialize() function call
+  // returns false, Deinitialize() will be called again to ensure we will
+  // initialize COM components again.
+  bool ResetAndInitialize();
+
+  // Resets all COM components to nullptr, so is_initialized() will return
+  // false.
+  void Deinitialize();
+
+  // Initializes default audio device related components. These components must
+  // be recreated once the default audio device changed. Returns false if
+  // initialization failed.
+  bool Initialize();
+
+  // Whether all components are correctly initialized. If last
+  // Initialize() function call failed, this function will return false.
+  // Otherwise this function will return true.
+  bool is_initialized() const;
+
   // Receives all packets from the audio capture endpoint buffer and pushes them
   // to the network.
   void DoCapture();
@@ -55,11 +79,14 @@ class AudioCapturerWin : public AudioCapturer {
   AudioSilenceDetector silence_detector_;
 
   base::win::ScopedCoMem<WAVEFORMATEX> wave_format_ex_;
+  base::win::ScopedComPtr<IMMDeviceEnumerator> mm_device_enumerator_;
   base::win::ScopedComPtr<IAudioCaptureClient> audio_capture_client_;
   base::win::ScopedComPtr<IAudioClient> audio_client_;
   base::win::ScopedComPtr<IMMDevice> mm_device_;
   base::win::ScopedComPtr<IAudioEndpointVolume> audio_volume_;
 
+  const std::unique_ptr<MMNotificationClient> mm_notification_client_;
+
   HRESULT last_capture_error_;
 
   base::ThreadChecker thread_checker_;