Enable -Winconsistent-missing-override flag.

webrtc/api/test/fakedtlsidentitystore.h

 /*
  *  Copyright 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 128 matching lines @@
     MSG_SUCCESS,
     MSG_FAILURE,
   };
 
   const char* get_key() {
     return kKeysAndCerts[key_index_].rsa_private_key_pem;
   }
   const char* get_cert() { return kKeysAndCerts[key_index_].cert_pem; }
 
   // rtc::MessageHandler implementation.
-  void OnMessage(rtc::Message* msg) {
+  void OnMessage(rtc::Message* msg) override {
     MessageData* message_data = static_cast<MessageData*>(msg->pdata);
     rtc::scoped_refptr<webrtc::DtlsIdentityRequestObserver> observer =
         message_data->data();
     switch (msg->message_id) {
       case MSG_SUCCESS: {
         std::string cert;
         std::string key;
         rtc::SSLIdentity::PemToDer("CERTIFICATE", get_cert(), &cert);
         rtc::SSLIdentity::PemToDer("RSA PRIVATE KEY", get_key(), &key);
         observer->OnSuccess(cert, key);
         break;
       }
       case MSG_FAILURE:
         observer->OnFailure(0);
         break;
     }
     delete message_data;
   }
 
   bool should_fail_;
   int key_index_ = 0;
 };
 
 #endif  // WEBRTC_API_TEST_FAKEDTLSIDENTITYSERVICE_H_