This CL adjusts the filter adaptation behavior to better handle reverberant environments and environments with poor SNR. It furthermore updates the unittests to handle the reduced adaptation speed. Bug: webrtc:8661 Change-Id: I5f1b5a4a34b333bd6c643ed3727899d0838dbf90 Reviewed-on: https://webrtc-review.googlesource.com/34184 Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org> Commit-Queue: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21323}