Balancing the transparency in AEC3 between saturating and low echo paths

This CL balances the NLP tradeoff in AEC3 to properly handle the cases
when the echo path is so strong that it saturates the echo and when it
is so weak that the echo is very low compared to nearend.

Bug: webrtc:8411, webrtc:8412, chromium:775653
Change-Id: I5aff74dfadd51cac1ce71b1cb935d68a5be6918d
Reviewed-on: https://webrtc-review.googlesource.com/14120
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20418}

modules/audio_processing/include/audio_processing.h

@@ -1188,7 +1188,7 @@ struct EchoCanceller3Config {
 
     GainChanges low_noise = {3.f, 3.f, 1.5f, 1.5f, 1.5f, 1.5f};
     GainChanges normal = {2.f, 2.f, 1.5f, 1.5f, 1.2f, 1.2f};
-    GainChanges saturation = {1.2f, 1.2f, 1.5f, 1.5f, 1.f, 1.f};
+    GainChanges saturation = {1.5f, 1.5f, 1.2f, 1.2f, 1.1f, 1.1f};
     GainChanges nonlinear = {1.5f, 1.5f, 1.2f, 1.2f, 1.1f, 1.1f};
 
     float floor_first_increase = 0.0001f;