Standardize usage of virtual/override/final in components/

components/gcm_driver/gcm_account_mapper.h

Index: components/gcm_driver/gcm_account_mapper.h
diff --git a/components/gcm_driver/gcm_account_mapper.h b/components/gcm_driver/gcm_account_mapper.h
index dc4c60137eb2493ce36ad4a4906e8a758cf34480..5616236dab409731dc3da05b6408eb8f9b503c30 100644
--- a/components/gcm_driver/gcm_account_mapper.h
+++ b/components/gcm_driver/gcm_account_mapper.h
@@ -31,7 +31,7 @@ class GCMAccountMapper : public GCMAppHandler {
   typedef std::vector<AccountMapping> AccountMappings;
 
   explicit GCMAccountMapper(GCMDriver* gcm_driver);
-  virtual ~GCMAccountMapper();
+  ~GCMAccountMapper() override;
 
   void Initialize(const AccountMappings& account_mappings);
 
@@ -41,16 +41,16 @@ class GCMAccountMapper : public GCMAppHandler {
       const std::vector<GCMClient::AccountTokenInfo>& account_tokens);
 
   // Implementation of 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;
-  virtual bool CanHandle(const std::string& app_id) const override;
+  void OnSendAcknowledged(const std::string& app_id,
+                          const std::string& message_id) override;
+  bool CanHandle(const std::string& app_id) const override;
 
  private:
   friend class GCMAccountMapperTest;