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..dd16e81318d5f8aff08de1da0ae622d6f13eccbc 100644
--- a/remoting/host/audio_capturer_win.h
+++ b/remoting/host/audio_capturer_win.h
@@ -33,6 +33,10 @@ class AudioCapturerWin : public AudioCapturer {
   // to the network.
   void DoCapture();
 
+  // Returns whether audio has been muted. If audio is not muted, this function
+  // sets level as the volume value with range (0.0, 1.0].
+  bool IsMuted(float* level);

[joedow, 2016/03/02 15:25:52]

It seems like this function is doing too much for its name, I wouldn't expect
IsMuted to also set audio volume.  It probably makes sense to break this into
two function or rename it to indicate that it will determine the audio level.

+
   PacketCapturedCallback callback_;
 
   AudioPacket::SamplingRate sampling_rate_;
@@ -46,6 +50,7 @@ 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_;