Standardize usage of virtual/override/final in media/

media/video/capture/mac/video_capture_device_mac.h

Index: media/video/capture/mac/video_capture_device_mac.h
diff --git a/media/video/capture/mac/video_capture_device_mac.h b/media/video/capture/mac/video_capture_device_mac.h
index ec902d38018d19db281e6396d4fd26285c156814..a3fd1b1061daad2e3756d8079a0a4d95f185a4f7 100644
--- a/media/video/capture/mac/video_capture_device_mac.h
+++ b/media/video/capture/mac/video_capture_device_mac.h
@@ -56,13 +56,12 @@ enum {
 class VideoCaptureDeviceMac : public VideoCaptureDevice {
  public:
   explicit VideoCaptureDeviceMac(const Name& device_name);
-  virtual ~VideoCaptureDeviceMac();
+  ~VideoCaptureDeviceMac() override;
 
   // VideoCaptureDevice implementation.
-  virtual void AllocateAndStart(
-      const VideoCaptureParams& params,
-      scoped_ptr<VideoCaptureDevice::Client> client) override;
-  virtual void StopAndDeAllocate() override;
+  void AllocateAndStart(const VideoCaptureParams& params,
+                        scoped_ptr<VideoCaptureDevice::Client> client) override;
+  void StopAndDeAllocate() override;
 
   bool Init(VideoCaptureDevice::Name::CaptureApiType capture_api_type);