WebRTC AEC Mobile (aka AECm) within the Audio Processing module has been unmaintained for some years and has been fully replaced by AEC3.
The ability to run AECm will be removed with this change, which was submitted to Chrome Canary M146 in January.. It will be followed by an AudioProcessing API change, a removal of the config mobile_mode, and then a removal of the AECm code.
If you were using AECm, you might want to use AEC3 echo canceller which is a better choice in all cases.