[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..5cc826aaa5b7505ce287c6a2575b78a1aa9ef7e9 100644
--- a/remoting/host/audio_capturer_win.h
+++ b/remoting/host/audio_capturer_win.h
@@ -31,6 +31,21 @@ 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;
+
+  // Resets and reinitializes default audio device related components. These
+  // components must be recreated once the default audio device changed. Returns
+  // false if initialization failed.
+  bool ResetAndInitialize();
+
+  // Whether all components are correctly initialized. If last
+  // ResetAndInitialize() function call failed, this function will return false.
+  // Otherwise this function will return true.
+  bool Initialized() const;
+
   // Receives all packets from the audio capture endpoint buffer and pushes them
   // to the network.
   void DoCapture();
@@ -55,11 +70,14 @@ 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_;