Standardize usage of virtual/override/final in components/

components/gcm_driver/default_gcm_app_handler.h

Index: components/gcm_driver/default_gcm_app_handler.h
diff --git a/components/gcm_driver/default_gcm_app_handler.h b/components/gcm_driver/default_gcm_app_handler.h
index ffe382b2fe4b52c7e4976a8c1b17b96a6720f954..bfe76a11d087f60aaf9138d6198fcbc4e9030aca 100644
--- a/components/gcm_driver/default_gcm_app_handler.h
+++ b/components/gcm_driver/default_gcm_app_handler.h
@@ -15,18 +15,18 @@ namespace gcm {
 class DefaultGCMAppHandler : public GCMAppHandler {
  public:
   DefaultGCMAppHandler();
-  virtual ~DefaultGCMAppHandler();
+  ~DefaultGCMAppHandler() override;
 
   // Overridden from GCMAppHandler:
-  virtual void ShutdownHandler() override;
-  virtual void OnMessage(const std::string& app_id,
-                         const GCMClient::IncomingMessage& message) override;
-  virtual void OnMessagesDeleted(const std::string& app_id) override;
-  virtual void OnSendError(
+  void ShutdownHandler() override;
+  void OnMessage(const std::string& app_id,
+                 const GCMClient::IncomingMessage& message) override;
+  void OnMessagesDeleted(const std::string& app_id) override;
+  void OnSendError(
       const std::string& app_id,
       const GCMClient::SendErrorDetails& send_error_details) override;
-  virtual void OnSendAcknowledged(const std::string& app_id,
-                                  const std::string& message_id) override;
+  void OnSendAcknowledged(const std::string& app_id,
+                          const std::string& message_id) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultGCMAppHandler);