Fix chromium-style warnings in webrtc/sound/.

webrtc/sound/nullsoundsystem.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_SOUND_NULLSOUNDSYSTEM_H_
 #define WEBRTC_SOUND_NULLSOUNDSYSTEM_H_
 
 #include "webrtc/sound/soundsysteminterface.h"
 
 namespace rtc {
 
 class SoundDeviceLocator;
 class SoundInputStreamInterface;
 class SoundOutputStreamInterface;
 
 // A simple reference sound system that drops output samples and generates
 // no input samples.
 class NullSoundSystem : public SoundSystemInterface {
  public:
   static SoundSystemInterface *Create() {
     return new NullSoundSystem();
   }
 
-  virtual ~NullSoundSystem();
+  ~NullSoundSystem() override;
 
-  virtual bool Init();
-  virtual void Terminate();
+  bool Init() override;
+  void Terminate() override;
 
-  virtual bool EnumeratePlaybackDevices(SoundDeviceLocatorList *devices);
-  virtual bool EnumerateCaptureDevices(SoundDeviceLocatorList *devices);
+  bool EnumeratePlaybackDevices(SoundDeviceLocatorList *devices) override;
+  bool EnumerateCaptureDevices(SoundDeviceLocatorList *devices) override;
 
-  virtual SoundOutputStreamInterface *OpenPlaybackDevice(
+  SoundOutputStreamInterface *OpenPlaybackDevice(
       const SoundDeviceLocator *device,
-      const OpenParams &params);
-  virtual SoundInputStreamInterface *OpenCaptureDevice(
+      const OpenParams &params) override;
+  SoundInputStreamInterface *OpenCaptureDevice(
       const SoundDeviceLocator *device,
-      const OpenParams &params);
+      const OpenParams &params) override;
 
-  virtual bool GetDefaultPlaybackDevice(SoundDeviceLocator **device);
-  virtual bool GetDefaultCaptureDevice(SoundDeviceLocator **device);
+  bool GetDefaultPlaybackDevice(SoundDeviceLocator **device) override;
+  bool GetDefaultCaptureDevice(SoundDeviceLocator **device) override;
 
-  virtual const char *GetName() const;
+  const char *GetName() const override;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_SOUND_NULLSOUNDSYSTEM_H_