Reason for revert: Seems to have broken Chromium tests. Original issue's description: > AcmReceiver: Look up last decoder in NetEq's table of decoders > > AcmReceiver::decoders_ is now one step closer to being unused. > > BUG=webrtc:5801 > > Committed: https://crrev.com/1e4d8b574cde64d93b98d89c7b817fb93185a307 > Cr-Commit-Position: refs/heads/master@{#14274} TBR=ossu@webrtc.org,henrik.lundin@webrtc.org # Skipping CQ checks because original CL landed less than 1 days ago. NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:5801 Review-Url: https://codereview.webrtc.org/2348123002 Cr-Commit-Position: refs/heads/master@{#14279}