Standardize usage of virtual/override/final in components/

components/gcm_driver/system_encryptor.h

Index: components/gcm_driver/system_encryptor.h
diff --git a/components/gcm_driver/system_encryptor.h b/components/gcm_driver/system_encryptor.h
index 48c75c84964d0cb9145cda6233d70afbe87ec233..02339ad55595992d338891587099a54690c39823 100644
--- a/components/gcm_driver/system_encryptor.h
+++ b/components/gcm_driver/system_encryptor.h
@@ -13,13 +13,13 @@ namespace gcm {
 // Encryptor that uses the Chrome password manager's encryptor.
 class SystemEncryptor : public 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 gcm