Removes unused WaveOut APIs from ADM

webrtc/modules/audio_device/include/audio_device.h

Index: webrtc/modules/audio_device/include/audio_device.h
diff --git a/webrtc/modules/audio_device/include/audio_device.h b/webrtc/modules/audio_device/include/audio_device.h
index 8fdd21246ea428f4812a9fdbf6c66853cd132d37..a1276d939203fd238a5c39bf70ffe1e2b4eb6c0b 100644
--- a/webrtc/modules/audio_device/include/audio_device.h
+++ b/webrtc/modules/audio_device/include/audio_device.h
@@ -108,11 +108,12 @@ class AudioDeviceModule : public RefCountedModule {
   virtual int32_t SetAGC(bool enable) = 0;
   virtual bool AGC() const = 0;
 
-  // Volume control based on the Windows Wave API (Windows only)
+  // Deprecated.
+  // TODO(henrika): to be removed.
   virtual int32_t SetWaveOutVolume(uint16_t volumeLeft,

[The Sun (google.com), 2017/08/29 12:56:43]

Is it possible to remove them directly? I can only see there being a problem if
an external impl uses "override".

-                                   uint16_t volumeRight) = 0;
+                                   uint16_t volumeRight) { return -1; }
   virtual int32_t WaveOutVolume(uint16_t* volumeLeft,
-                                uint16_t* volumeRight) const = 0;
+                                uint16_t* volumeRight) const { return -1; }
 
   // Audio mixer initialization
   virtual int32_t InitSpeaker() = 0;