Enable -Winconsistent-missing-override flag.

webrtc/modules/audio_coding/acm2/acm_send_test_oldapi.h

 /*
  *  Copyright (c) 2014 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 29 matching lines @@
                      int channels,
                      int payload_type,
                      int frame_size_samples);
 
   // Registers an external send codec. Returns true on success, false otherwise.
   bool RegisterExternalCodec(AudioEncoder* external_speech_encoder);
 
   // Returns the next encoded packet. Returns NULL if the test duration was
   // exceeded. Ownership of the packet is handed over to the caller.
   // Inherited from PacketSource.
-  Packet* NextPacket();
+  Packet* NextPacket() override;
 
   // Inherited from AudioPacketizationCallback.
   int32_t SendData(FrameType frame_type,
                    uint8_t payload_type,
                    uint32_t timestamp,
                    const uint8_t* payload_data,
                    size_t payload_len_bytes,
                    const RTPFragmentationHeader* fragmentation) override;
 
   AudioCodingModule* acm() { return acm_.get(); }
@@ skipping 21 matching lines @@
   uint16_t sequence_number_;
   std::vector<uint8_t> last_payload_vec_;
   bool data_to_send_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AcmSendTestOldApi);
 };
 
 }  // namespace test
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_ACM2_ACM_SEND_TEST_OLDAPI_H_