Standardize usage of virtual/override/final in content/

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 541cb8f2957495e776fe94235bf84af3b45f66dc..84beac0dd6f0f1721dc67d0204539da9246c54be 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -143,12 +143,12 @@ class ConvertableToTraceFormatWrapper
   explicit ConvertableToTraceFormatWrapper(
       const blink::WebConvertableToTraceFormat& convertable)
       : convertable_(convertable) {}
-  virtual void AppendAsTraceFormat(std::string* out) const override {
+  void AppendAsTraceFormat(std::string* out) const override {
     *out += convertable_.asTraceFormat().utf8();
   }
 
  private:
-  virtual ~ConvertableToTraceFormatWrapper() {}
+  ~ConvertableToTraceFormatWrapper() override {}
 
   blink::WebConvertableToTraceFormat convertable_;
 };