[Chromoting] Move DefaultAudioDeviceChangeDetector out of AudioCapturerWin

remoting/host/win/default_audio_device_change_detector.h

Index: remoting/host/win/default_audio_device_change_detector.h
diff --git a/remoting/host/win/default_audio_device_change_detector.h b/remoting/host/win/default_audio_device_change_detector.h
new file mode 100644
index 0000000000000000000000000000000000000000..c38df3f82c1ceccea21a43141b9713293255712f
--- /dev/null
+++ b/remoting/host/win/default_audio_device_change_detector.h
@@ -0,0 +1,54 @@
+// Copyright 2017 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_WIN_DEFAULT_AUDIO_DEVICE_CHANGE_DETECTOR_H_
+#define REMOTING_HOST_WIN_DEFAULT_AUDIO_DEVICE_CHANGE_DETECTOR_H_
+
+#include <mmdeviceapi.h>
+
+#include "base/synchronization/lock.h"
+#include "base/win/scoped_comptr.h"
+
+namespace remoting {
+
+// An IMMNotificationClient implementation to detect the change of the default
+// audio output device on the system. It registers itself into the input
+// IMMDeviceEnumerator in constructor and unregisters in destructor.
+// This class does not use the default ref-counting memory management method
+// provided by IUnknown: calling DefaultAudioDeviceChangeDetector::Release()
+// won't delete the object.
+class DefaultAudioDeviceChangeDetector final : public IMMNotificationClient {
+ public:
+  explicit DefaultAudioDeviceChangeDetector(
+      const base::win::ScopedComPtr<IMMDeviceEnumerator>& enumerator);
+  ~DefaultAudioDeviceChangeDetector();
+
+  bool GetAndReset();
+
+ private:
+  // IMMNotificationClient implementation.
+  HRESULT __stdcall OnDefaultDeviceChanged(EDataFlow flow,
+                                           ERole role,
+                                           LPCWSTR pwstrDefaultDevice) override;
+
+  HRESULT __stdcall QueryInterface(REFIID iid, void** object) override;
+
+  // No-ops overrides.
+  HRESULT __stdcall OnDeviceAdded(LPCWSTR pwstrDeviceId) override;
+  HRESULT __stdcall OnDeviceRemoved(LPCWSTR pwstrDeviceId) override;
+  HRESULT __stdcall OnDeviceStateChanged(LPCWSTR pwstrDeviceId,
+                                         DWORD dwNewState) override;
+  HRESULT __stdcall OnPropertyValueChanged(LPCWSTR pwstrDeviceId,
+                                           const PROPERTYKEY key) override;
+  ULONG __stdcall AddRef() override;
+  ULONG __stdcall Release() override;
+
+  const base::win::ScopedComPtr<IMMDeviceEnumerator> enumerator_;
+  bool changed_ = false;
+  base::Lock lock_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_WIN_DEFAULT_AUDIO_DEVICE_CHANGE_DETECTOR_H_