This is from the upstream library commit id 3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium 88.0.4290.1.
This new lib contains the bare minimum to implement an iSAC encoder and decoder. The webrtc files have been copied from the revision as the existing imported files (c8b569e0a7ad0b369e15f0197b3a558699ec8efa).