This CL adds some general AEC3 transparency improvements. Specifically: -A minimum for how the nearend is masking echo is added. -A temporal smoothing constant is increased to increase the transparency. -Parameters are surfaced to the parameter config struct. Bug: webrtc:8360 Change-Id: I2a4881eb40f4fab53ad740c4001925f0af86bbec Reviewed-on: https://webrtc-review.googlesource.com/7605 Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org> Commit-Queue: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20200}