Fix chromium-style warnings in webrtc/sound/.

webrtc/sound/alsasoundsystem.h

Index: webrtc/sound/alsasoundsystem.h
diff --git a/webrtc/sound/alsasoundsystem.h b/webrtc/sound/alsasoundsystem.h
index b0cc1a4029ba6b64a19235a3fe5f26adf2830e96..dbf34d178b265f44f3c3511f2630115f2755d639 100644
--- a/webrtc/sound/alsasoundsystem.h
+++ b/webrtc/sound/alsasoundsystem.h
@@ -34,25 +34,25 @@ class AlsaSoundSystem : public SoundSystemInterface {
 
   AlsaSoundSystem();
 
-  virtual ~AlsaSoundSystem();
+  ~AlsaSoundSystem() 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 bool GetDefaultPlaybackDevice(SoundDeviceLocator **device);
-  virtual bool GetDefaultCaptureDevice(SoundDeviceLocator **device);
+  bool GetDefaultPlaybackDevice(SoundDeviceLocator **device) override;
+  bool GetDefaultCaptureDevice(SoundDeviceLocator **device) 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 const char *GetName() const;
+  const char *GetName() const override;
 
  private:
   bool IsInitialized() { return initialized_; }