Standardize usage of virtual/override/final specifiers.

ash/shell/content_client/shell_browser_main_parts.h

Index: ash/shell/content_client/shell_browser_main_parts.h
diff --git a/ash/shell/content_client/shell_browser_main_parts.h b/ash/shell/content_client/shell_browser_main_parts.h
index 757c818fc372033837d210c92456e2eb6b57f3d0..89684315c50dd297913f874bc9d1850a028ca004 100644
--- a/ash/shell/content_client/shell_browser_main_parts.h
+++ b/ash/shell/content_client/shell_browser_main_parts.h
@@ -36,15 +36,15 @@ class ShellBrowserMainParts : public content::BrowserMainParts {
  public:
   explicit ShellBrowserMainParts(
       const content::MainFunctionParams& parameters);
-  virtual ~ShellBrowserMainParts();
+  ~ShellBrowserMainParts() override;
 
   // Overridden from content::BrowserMainParts:
-  virtual void PreMainMessageLoopStart() override;
-  virtual void PostMainMessageLoopStart() override;
-  virtual void ToolkitInitialized() override;
-  virtual void PreMainMessageLoopRun() override;
-  virtual bool MainMessageLoopRun(int* result_code) override;
-  virtual void PostMainMessageLoopRun() override;
+  void PreMainMessageLoopStart() override;
+  void PostMainMessageLoopStart() override;
+  void ToolkitInitialized() override;
+  void PreMainMessageLoopRun() override;
+  bool MainMessageLoopRun(int* result_code) override;
+  void PostMainMessageLoopRun() override;
 
   content::ShellBrowserContext* browser_context() {
     return browser_context_.get();