Revert of Enable -Winconsistent-missing-override flag.

webrtc/modules/video_coding/codecs/vp8/simulcast_unittest.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 150 matching lines @@
     return configured_bitrates;
   }
 
   class SpyingTemporalLayers : public TemporalLayers {
    public:
     explicit SpyingTemporalLayers(TemporalLayers* layers)
         : configured_bitrate_(0), layers_(layers) {}
 
     virtual ~SpyingTemporalLayers() { delete layers_; }
 
-    int EncodeFlags(uint32_t timestamp) override {
+    virtual int EncodeFlags(uint32_t timestamp) {
       return layers_->EncodeFlags(timestamp);
     }
 
     bool ConfigureBitrates(int bitrate_kbit,
                            int max_bitrate_kbit,
                            int framerate,
                            vpx_codec_enc_cfg_t* cfg) override {
       configured_bitrate_ = bitrate_kbit;
       return layers_->ConfigureBitrates(bitrate_kbit, max_bitrate_kbit,
                                         framerate, cfg);
@@ skipping 766 matching lines @@
   std::unique_ptr<VP8Decoder> decoder_;
   MockDecodedImageCallback decoder_callback_;
   VideoCodec settings_;
   VideoFrame input_frame_;
 };
 
 }  // namespace testing
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_CODECS_VP8_SIMULCAST_UNITTEST_H_