Update {virtual,override,final} to follow C++11 style.

chrome/browser/android/webapps/single_tab_mode_tab_helper.h

Index: chrome/browser/android/webapps/single_tab_mode_tab_helper.h
diff --git a/chrome/browser/android/webapps/single_tab_mode_tab_helper.h b/chrome/browser/android/webapps/single_tab_mode_tab_helper.h
index a79fd2e4359d3f7cb7348efe1520dadebe206d1c..744aee3da4238007b55e8ae6d66c2adff51c8e61 100644
--- a/chrome/browser/android/webapps/single_tab_mode_tab_helper.h
+++ b/chrome/browser/android/webapps/single_tab_mode_tab_helper.h
@@ -30,7 +30,7 @@ class SingleTabModeTabHelper
   // Checks if the ID pair is blocked from creating new windows. IO-thread only.
   static bool IsRegistered(int32 process_id, int32 routing_id);
 
-  virtual ~SingleTabModeTabHelper();
+  ~SingleTabModeTabHelper() override;
 
   // Handles opening the given URL through the TabModel.
   void HandleOpenUrl(const BlockedWindowParams& params);
@@ -40,10 +40,8 @@ class SingleTabModeTabHelper
   void PermanentlyBlockAllNewWindows();
 
   // content::WebContentsObserver
-  virtual void RenderViewCreated(content::RenderViewHost* render_view_host)
-      override;
-  virtual void RenderViewDeleted(content::RenderViewHost* render_view_host)
-      override;
+  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
+  void RenderViewDeleted(content::RenderViewHost* render_view_host) override;
 
  private:
   explicit SingleTabModeTabHelper(content::WebContents* web_contents);