This CL adds a DCHECK for the deprecated 8 kHz rate in APM. It also updates the agc fuzzer code to properly do band-split on the signals, and not send 8 kHz signals into the AGC. Bug: chromium:1028092,chromium:1028172 Change-Id: I1e7c8d721834310e94b0e21efea07f75da837cab Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160600 Reviewed-by: Sam Zackrisson <saza@webrtc.org> Commit-Queue: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29914}