MockAudioEncoder: Use a dedicated marker method for test expectations

webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h

Index: webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
diff --git a/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h b/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
index a34edb3150ba197dc419ddb81c403e10a71d121a..95426d89e1efe7b85368f909efbee5974d8246de 100644
--- a/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
+++ b/webrtc/modules/audio_coding/codecs/mock/mock_audio_encoder.h
@@ -21,6 +21,7 @@ class MockAudioEncoder final : public AudioEncoder {
  public:
   ~MockAudioEncoder() override { Die(); }
   MOCK_METHOD0(Die, void());
+  MOCK_METHOD1(Mark, void(std::string desc));
   MOCK_CONST_METHOD0(MaxEncodedBytes, size_t());
   MOCK_CONST_METHOD0(SampleRateHz, int());
   MOCK_CONST_METHOD0(NumChannels, int());