Remove saturation warning support from TransmitMixer.

BUG=none

Review-Url: https://codereview.webrtc.org/2720253002
Cr-Original-Commit-Position: refs/heads/master@{#16913}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ba08a140da6cee478c62cf61e857cfee1647bf95
4 files changed