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/api/test/fakeaudiocapturemodule.h b/webrtc/api/test/fakeaudiocapturemodule.h
index 30ad3f8..098243f 100644
--- a/webrtc/api/test/fakeaudiocapturemodule.h
+++ b/webrtc/api/test/fakeaudiocapturemodule.h
@@ -174,12 +174,12 @@
   int32_t ResetAudioDevice() override;
   int32_t SetLoudspeakerStatus(bool enable) override;
   int32_t GetLoudspeakerStatus(bool* enabled) const override;
-  virtual bool BuiltInAECIsAvailable() const { return false; }
-  virtual int32_t EnableBuiltInAEC(bool enable) { return -1; }
-  virtual bool BuiltInAGCIsAvailable() const { return false; }
-  virtual int32_t EnableBuiltInAGC(bool enable) { return -1; }
-  virtual bool BuiltInNSIsAvailable() const { return false; }
-  virtual int32_t EnableBuiltInNS(bool enable) { return -1; }
+  bool BuiltInAECIsAvailable() const override { return false; }
+  int32_t EnableBuiltInAEC(bool enable) override { return -1; }
+  bool BuiltInAGCIsAvailable() const override { return false; }
+  int32_t EnableBuiltInAGC(bool enable) override { return -1; }
+  bool BuiltInNSIsAvailable() const override { return false; }
+  int32_t EnableBuiltInNS(bool enable) override { return -1; }
   // End of functions inherited from webrtc::AudioDeviceModule.
 
   // The following function is inherited from rtc::MessageHandler.
diff --git a/webrtc/api/test/fakeaudiocapturemodule_unittest.cc b/webrtc/api/test/fakeaudiocapturemodule_unittest.cc
index 8ac1acc..d0dcd85 100644
--- a/webrtc/api/test/fakeaudiocapturemodule_unittest.cc
+++ b/webrtc/api/test/fakeaudiocapturemodule_unittest.cc
@@ -31,7 +31,7 @@
     memset(rec_buffer_, 0, sizeof(rec_buffer_));
   }
 
-  virtual void SetUp() {
+  void SetUp() override {
     fake_audio_capture_module_ = FakeAudioCaptureModule::Create();
     EXPECT_TRUE(fake_audio_capture_module_.get() != NULL);
   }
diff --git a/webrtc/api/test/fakedtlsidentitystore.h b/webrtc/api/test/fakedtlsidentitystore.h
index 89c4084..c6f5a3c 100644
--- a/webrtc/api/test/fakedtlsidentitystore.h
+++ b/webrtc/api/test/fakedtlsidentitystore.h
@@ -146,7 +146,7 @@
   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();