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

content/renderer/manifest/manifest_manager.h

Index: content/renderer/manifest/manifest_manager.h
diff --git a/content/renderer/manifest/manifest_manager.h b/content/renderer/manifest/manifest_manager.h
index bae1fef6a10c88ba76905ae0e965ebda36231c35..5874724e695e09684214e6c09d07ab183d975c4c 100644
--- a/content/renderer/manifest/manifest_manager.h
+++ b/content/renderer/manifest/manifest_manager.h
@@ -33,15 +33,15 @@ class ManifestManager : public RenderFrameObserver {
   typedef base::Callback<void(const Manifest&)> GetManifestCallback;
 
   explicit ManifestManager(RenderFrame* render_frame);
-  virtual ~ManifestManager();
+  ~ManifestManager() override;
 
   // Will call the given |callback| with the Manifest associated with the
   // RenderFrame if any. Will pass an empty Manifest in case of error.
   void GetManifest(const GetManifestCallback& callback);
 
   // RenderFrameObserver implementation.
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
-  virtual void DidChangeManifest() override;
+  bool OnMessageReceived(const IPC::Message& message) override;
+  void DidChangeManifest() override;
 
  private:
   enum ResolveState {