Standardize usage of virtual/override/final in components/

components/sync_driver/system_encryptor.h

Index: components/sync_driver/system_encryptor.h
diff --git a/components/sync_driver/system_encryptor.h b/components/sync_driver/system_encryptor.h
index bdb7feac65fbb4b513d9305039bf7b880d98881d..7b08a5436d47334771c4ffc5385fb03a5aa2e5ca 100644
--- a/components/sync_driver/system_encryptor.h
+++ b/components/sync_driver/system_encryptor.h
@@ -13,13 +13,13 @@ namespace sync_driver {
 // Encryptor that uses the Chrome password manager's encryptor.
 class SystemEncryptor : public syncer::Encryptor {
  public:
-  virtual ~SystemEncryptor();
+  ~SystemEncryptor() override;
 
-  virtual bool EncryptString(const std::string& plaintext,
-                             std::string* ciphertext) override;
+  bool EncryptString(const std::string& plaintext,
+                     std::string* ciphertext) override;
 
-  virtual bool DecryptString(const std::string& ciphertext,
-                             std::string* plaintext) override;
+  bool DecryptString(const std::string& ciphertext,
+                     std::string* plaintext) override;
 };
 
 }  // namespace sync_driver