Enable -Winconsistent-missing-override flag.

The problem with gmock is worked around by commenting out any other override declarations in classes using gmock.

NOPRESUBMIT=True
BUG=webrtc:3970

Review-Url: https://codereview.webrtc.org/1921653002
Cr-Commit-Position: refs/heads/master@{#12563}
diff --git a/webrtc/modules/video_coding/codecs/vp8/realtime_temporal_layers.cc b/webrtc/modules/video_coding/codecs/vp8/realtime_temporal_layers.cc
index d226013..b9721cd 100644
--- a/webrtc/modules/video_coding/codecs/vp8/realtime_temporal_layers.cc
+++ b/webrtc/modules/video_coding/codecs/vp8/realtime_temporal_layers.cc
@@ -101,10 +101,10 @@
 
   virtual ~RealTimeTemporalLayers() {}
 
-  virtual bool ConfigureBitrates(int bitrate_kbit,
-                                 int max_bitrate_kbit,
-                                 int framerate,
-                                 vpx_codec_enc_cfg_t* cfg) {
+  bool ConfigureBitrates(int bitrate_kbit,
+                         int max_bitrate_kbit,
+                         int framerate,
+                         vpx_codec_enc_cfg_t* cfg) override {
     temporal_layers_ =
         CalculateNumberOfTemporalLayers(temporal_layers_, framerate);
     temporal_layers_ = std::min(temporal_layers_, max_temporal_layers_);
@@ -184,7 +184,7 @@
     return true;
   }
 
-  virtual int EncodeFlags(uint32_t timestamp) {
+  int EncodeFlags(uint32_t timestamp) override {
     frame_counter_++;
     return CurrentEncodeFlags();
   }
@@ -196,16 +196,16 @@
     return encode_flags_[index];
   }
 
-  virtual int CurrentLayerId() const {
+  int CurrentLayerId() const override {
     assert(layer_ids_length_ > 0 && layer_ids_ != NULL);
     int index = frame_counter_ % layer_ids_length_;
     assert(index >= 0 && index < layer_ids_length_);
     return layer_ids_[index];
   }
 
-  virtual void PopulateCodecSpecific(bool base_layer_sync,
-                                     CodecSpecificInfoVP8* vp8_info,
-                                     uint32_t timestamp) {
+  void PopulateCodecSpecific(bool base_layer_sync,
+                             CodecSpecificInfoVP8* vp8_info,
+                             uint32_t timestamp) override {
     assert(temporal_layers_ > 0);
 
     if (temporal_layers_ == 1) {
diff --git a/webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter_unittest.cc b/webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter_unittest.cc
index 9a7e1b2..aafcd79 100644
--- a/webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter_unittest.cc
+++ b/webrtc/modules/video_coding/codecs/vp8/simulcast_encoder_adapter_unittest.cc
@@ -107,34 +107,40 @@
 
 class MockVideoEncoder : public VideoEncoder {
  public:
+  // TODO(nisse): Valid overrides commented out, because the gmock
+  // methods don't use any override declarations, and we want to avoid
+  // warnings from -Winconsistent-missing-override. See
+  // http://crbug.com/428099.
   int32_t InitEncode(const VideoCodec* codecSettings,
                      int32_t numberOfCores,
-                     size_t maxPayloadSize) override {
+                     size_t maxPayloadSize) /* override */ {
     codec_ = *codecSettings;
     return 0;
   }
 
   int32_t Encode(const VideoFrame& inputImage,
                  const CodecSpecificInfo* codecSpecificInfo,
-                 const std::vector<FrameType>* frame_types) override {
+                 const std::vector<FrameType>* frame_types) /* override */ {
     return 0;
   }
 
   int32_t RegisterEncodeCompleteCallback(
-      EncodedImageCallback* callback) override {
+      EncodedImageCallback* callback) /* override */ {
     callback_ = callback;
     return 0;
   }
 
-  int32_t Release() override { return 0; }
+  int32_t Release() /* override */ { return 0; }
 
-  int32_t SetRates(uint32_t newBitRate, uint32_t frameRate) override {
+  int32_t SetRates(uint32_t newBitRate, uint32_t frameRate) /* override */ {
     return 0;
   }
 
   MOCK_METHOD2(SetChannelParameters, int32_t(uint32_t packetLoss, int64_t rtt));
 
-  bool SupportsNativeHandle() const override { return supports_native_handle_; }
+  bool SupportsNativeHandle() const /* override */ {
+    return supports_native_handle_;
+  }
 
   virtual ~MockVideoEncoder() {}
 
diff --git a/webrtc/modules/video_coding/codecs/vp8/simulcast_unittest.h b/webrtc/modules/video_coding/codecs/vp8/simulcast_unittest.h
index 2b2aa5d..8d5b74f 100644
--- a/webrtc/modules/video_coding/codecs/vp8/simulcast_unittest.h
+++ b/webrtc/modules/video_coding/codecs/vp8/simulcast_unittest.h
@@ -168,7 +168,7 @@
 
     virtual ~SpyingTemporalLayers() { delete layers_; }
 
-    virtual int EncodeFlags(uint32_t timestamp) {
+    int EncodeFlags(uint32_t timestamp) override {
       return layers_->EncodeFlags(timestamp);
     }
 
diff --git a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
index 6906a32..f8af642 100644
--- a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
+++ b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.h
@@ -40,21 +40,21 @@
 
   virtual ~VP8EncoderImpl();
 
-  virtual int Release();
+  int Release() override;
 
-  virtual int InitEncode(const VideoCodec* codec_settings,
-                         int number_of_cores,
-                         size_t max_payload_size);
+  int InitEncode(const VideoCodec* codec_settings,
+                 int number_of_cores,
+                 size_t max_payload_size) override;
 
-  virtual int Encode(const VideoFrame& input_image,
-                     const CodecSpecificInfo* codec_specific_info,
-                     const std::vector<FrameType>* frame_types);
+  int Encode(const VideoFrame& input_image,
+             const CodecSpecificInfo* codec_specific_info,
+             const std::vector<FrameType>* frame_types) override;
 
-  virtual int RegisterEncodeCompleteCallback(EncodedImageCallback* callback);
+  int RegisterEncodeCompleteCallback(EncodedImageCallback* callback) override;
 
-  virtual int SetChannelParameters(uint32_t packet_loss, int64_t rtt);
+  int SetChannelParameters(uint32_t packet_loss, int64_t rtt) override;
 
-  virtual int SetRates(uint32_t new_bitrate_kbit, uint32_t frame_rate);
+  int SetRates(uint32_t new_bitrate_kbit, uint32_t frame_rate) override;
 
   void OnDroppedFrame() override {}
 
diff --git a/webrtc/modules/video_coding/jitter_buffer_unittest.cc b/webrtc/modules/video_coding/jitter_buffer_unittest.cc
index eb7d78b..af9c20a 100644
--- a/webrtc/modules/video_coding/jitter_buffer_unittest.cc
+++ b/webrtc/modules/video_coding/jitter_buffer_unittest.cc
@@ -215,7 +215,7 @@
 
  protected:
   TestBasicJitterBuffer() : scoped_field_trial_(GetParam()) {}
-  virtual void SetUp() {
+  void SetUp() override {
     clock_.reset(new SimulatedClock(0));
     jitter_buffer_.reset(new VCMJitterBuffer(
         clock_.get(),