This CL adds two kill-switches to the AEC3 code to be used as safe fallbacks to increase AEC transparency. The changes have been shown to be bitexact for a test dataset. Bug: webrtc:11487,chromium:1067597 Change-Id: I7f9f78db4964990bcdfa9adae6ef36a56bce7224 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/172840 Reviewed-by: Sam Zackrisson <saza@webrtc.org> Commit-Queue: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#30998}