Standardize usage of virtual/override/final specifiers.

extensions/shell/test/shell_test.h

Index: extensions/shell/test/shell_test.h
diff --git a/extensions/shell/test/shell_test.h b/extensions/shell/test/shell_test.h
index 286299d2604313ceb704b64cd704df7be9f2d607..fab2d151610b4fcd0f6140fc181c7848b8f2cabb 100644
--- a/extensions/shell/test/shell_test.h
+++ b/extensions/shell/test/shell_test.h
@@ -25,10 +25,10 @@ class ShellExtensionSystem;
 class AppShellTest : public content::BrowserTestBase {
  public:
   AppShellTest();
-  virtual ~AppShellTest();
+  ~AppShellTest() override;
 
   // content::BrowserTestBase implementation.
-  virtual void SetUp() override;
+  void SetUp() override;
   void SetUpOnMainThread() override;
   void RunTestOnMainThreadLoop() override;