This CL changes the downmixing of the input to the delay estimation for surround/stereo signals to be off by default. A kill-switch is also added for enforcing the downmix to be on. Bug: webrtc:10913 Change-Id: I1030fef593ba56416deeb13b80d2f3812bffb9ed Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161012 Commit-Queue: Per Åhgren <peah@webrtc.org> Commit-Queue: Sam Zackrisson <saza@webrtc.org> Reviewed-by: Sam Zackrisson <saza@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29951}