Standardize usage of virtual/override/final specifiers.

extensions/shell/browser/shell_browser_main_parts.h

Index: extensions/shell/browser/shell_browser_main_parts.h
diff --git a/extensions/shell/browser/shell_browser_main_parts.h b/extensions/shell/browser/shell_browser_main_parts.h
index 614601468bded86a8143ab075dcd2664c5270c9c..8e4d1eff73ce04e32fc5eebc6e5091056d6ca1bb 100644
--- a/extensions/shell/browser/shell_browser_main_parts.h
+++ b/extensions/shell/browser/shell_browser_main_parts.h
@@ -47,21 +47,21 @@ class ShellBrowserMainParts : public content::BrowserMainParts {
  public:
   ShellBrowserMainParts(const content::MainFunctionParams& parameters,
                         ShellBrowserMainDelegate* browser_main_delegate);
-  virtual ~ShellBrowserMainParts();
+  ~ShellBrowserMainParts() override;
 
   ShellBrowserContext* browser_context() { return browser_context_.get(); }
 
   ShellExtensionSystem* extension_system() { return extension_system_; }
 
   // BrowserMainParts overrides.
-  virtual void PreEarlyInitialization() override;
-  virtual void PreMainMessageLoopStart() override;
-  virtual void PostMainMessageLoopStart() override;
-  virtual int PreCreateThreads() override;
-  virtual void PreMainMessageLoopRun() override;
-  virtual bool MainMessageLoopRun(int* result_code) override;
-  virtual void PostMainMessageLoopRun() override;
-  virtual void PostDestroyThreads() override;
+  void PreEarlyInitialization() override;
+  void PreMainMessageLoopStart() override;
+  void PostMainMessageLoopStart() override;
+  int PreCreateThreads() override;
+  void PreMainMessageLoopRun() override;
+  bool MainMessageLoopRun(int* result_code) override;
+  void PostMainMessageLoopRun() override;
+  void PostDestroyThreads() override;
 
  private:
   // Creates and initializes the ExtensionSystem.