The media_unittest NewByPts/MSEPipelineIntegrationTest.ConfigChange_EncryptedThenClear_MP4_CENC/0 currently succeeds, but outputs an error:
    [203153:203153:0223/172354.853883:2077859217483:ERROR:mp4_stream_parser.cc(189)] Error while parsing MP4

It appears that this error happens as the audio stream doesn't match the mimetype [1]. However, the comment in the test states "Config changes from encrypted to clear are not currently supported." [2].

From wolenetz@:
For MSE, the number and media type of tracks must match across all initialization segments (read: "MOOV" box, typically one per mp4 "file") appended to a SourceBuffer. If you append a v_frag (video-track-only file) and an av_frag (audio and video track file) to the same SourceBuffer, then you'll get that parse error; this is independent of any EME concerns like clear/encrypted that it appears is the intended focus of the test(s).

The test should be updated to simply append video only files.

[1] https://cs.chromium.org/chromium/src/media/formats/mp4/mp4_stream_parser.cc?l=339
[2] https://cs.chromium.org/chromium/src/media/test/pipeline_integration_test.cc?l=1950