Add volume control for windows host

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 de3c7953229704ee612ac08ff1d30385549d61cb..11070bef23bdd0c4e06f14b28842a51cd9bab6e4 100644
--- a/remoting/host/audio_capturer_win.h
+++ b/remoting/host/audio_capturer_win.h
@@ -33,6 +33,16 @@ class AudioCapturerWin : public AudioCapturer {
   // to the network.
   void DoCapture();
 
+  // Returns current volume setting of the host, in range [0.0, 1.0]. If the
+  // audio has been muted, this function returns 0. If Windows API returns error
+  // (such as audio device has been disabled or unpluged), this function ignores
+  // host volume setting, and returns 1.0.
+  float GetAudioLevel();
+
+  // Processes a series of samples, and executes callback if the packet is
+  // qualified to be sent to client.
+  void ProcessSamples(uint8_t* data, size_t frames, int32_t flags);
+
   PacketCapturedCallback callback_;
 
   AudioPacket::SamplingRate sampling_rate_;
@@ -46,6 +56,7 @@ class AudioCapturerWin : public AudioCapturer {
   base::win::ScopedComPtr<IAudioCaptureClient> audio_capture_client_;
   base::win::ScopedComPtr<IAudioClient> audio_client_;
   base::win::ScopedComPtr<IMMDevice> mm_device_;
+  base::win::ScopedComPtr<ISimpleAudioVolume> audio_volume_;
 
   HRESULT last_capture_error_;