Standardize usage of virtual/override/final in content/renderer/

content/renderer/mhtml_generator.h

Index: content/renderer/mhtml_generator.h
diff --git a/content/renderer/mhtml_generator.h b/content/renderer/mhtml_generator.h
index e308f3514fae5413b9e57429546b5ca30d26fb55..8a65b46afb4c819844b9b64e41176fd2bfb8092a 100644
--- a/content/renderer/mhtml_generator.h
+++ b/content/renderer/mhtml_generator.h
@@ -15,11 +15,11 @@ class RenderViewImpl;
 class MHTMLGenerator : public RenderViewObserver {
  public:
   explicit MHTMLGenerator(RenderViewImpl* render_view);
-  virtual ~MHTMLGenerator();
+  ~MHTMLGenerator() override;
 
  private:
   // RenderViewObserver implementation:
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
+  bool OnMessageReceived(const IPC::Message& message) override;
 
   void OnSavePageAsMHTML(int job_id,
                          IPC::PlatformFileForTransit file_for_transit);