Standardize usage of virtual/override/final in gin/

gin/public/v8_platform.h

Index: gin/public/v8_platform.h
diff --git a/gin/public/v8_platform.h b/gin/public/v8_platform.h
index 59e21479f53d12c49d892868b6f8d7334768c08d..a4fc28a9bc32cf394af4027cddfc116a85219fd1 100644
--- a/gin/public/v8_platform.h
+++ b/gin/public/v8_platform.h
@@ -19,17 +19,17 @@ class GIN_EXPORT V8Platform : public NON_EXPORTED_BASE(v8::Platform) {
   static V8Platform* Get();
 
   // v8::Platform implementation.
-  virtual void CallOnBackgroundThread(
+  void CallOnBackgroundThread(
       v8::Task* task,
       v8::Platform::ExpectedRuntime expected_runtime) override;
-  virtual void CallOnForegroundThread(v8::Isolate* isolate,
-                                      v8::Task* task) override;
-  virtual double MonotonicallyIncreasingTime() override;
+  void CallOnForegroundThread(v8::Isolate* isolate, v8::Task* task) override;
+  double MonotonicallyIncreasingTime() override;
+
  private:
   friend struct base::DefaultLazyInstanceTraits<V8Platform>;
 
   V8Platform();
-  virtual ~V8Platform();
+  ~V8Platform() override;
 
   DISALLOW_COPY_AND_ASSIGN(V8Platform);
 };