Add volume control for windows host

remoting/host/audio_capturer_win.h

 // Copyright (c) 2012 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.
 
 #ifndef REMOTING_HOST_AUDIO_CAPTURER_WIN_H_
 #define REMOTING_HOST_AUDIO_CAPTURER_WIN_H_
 
 #include <audioclient.h>
 #include <mmdeviceapi.h>
 
@@ skipping 15 matching lines @@
   ~AudioCapturerWin() override;
 
   // AudioCapturer interface.
   bool Start(const PacketCapturedCallback& callback) override;
 
  private:
   // Receives all packets from the audio capture endpoint buffer and pushes them
   // 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_;
 
   scoped_ptr<base::RepeatingTimer> capture_timer_;
   base::TimeDelta audio_device_period_;
 
   AudioSilenceDetector silence_detector_;
 
   base::win::ScopedCoMem<WAVEFORMATEX> wave_format_ex_;
   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_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioCapturerWin);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_AUDIO_CAPTURER_WIN_H_