In short, what I did was to
* Remove acm_common_defs.h (the stuff in it was used only by
acm_codec_database.cc).
* Move audio_coding_module_typedefs.h to a new build target.
* Move the NetEqDecoder enum (and the associated
NetEqDecoderToSdpAudioFormat function) to a new file in a new
build target.
BUG=webrtc:7243, webrtc:7244
Review-Url: https://codereview.webrtc.org/2723253005
Cr-Commit-Position: refs/heads/master@{#17005}