This CL adds and wires up a parameter (namely, adjacent speech frames threshold) used in `AdaptiveDigitalGainApplier`. Tested: bit-exactness verified with audioproc_f Bug: webrtc:7494 Change-Id: I751cd91f08a6e98ee20f767c8df0ed121c8d4b68 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/186049 Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Reviewed-by: Sam Zackrisson <saza@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32264}