Reason for revert: tommi pointed out that using a refptr for the sink may cause issues. Will reland with a slightly different approach. Original issue's description: > Storing raw audio sink for default audio track. > > BUG=webrtc:5250 > > Committed: https://crrev.com/e591f9377f33f3f725a30faecd1bef1a71fa6b99 > Cr-Commit-Position: refs/heads/master@{#11230} TBR=pthatcher@webrtc.org,solenberg@webrtc.org,pbos@webrtc.org,tommi@webrtc.org # Skipping CQ checks because original CL landed less than 1 days ago. NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:5250 Review URL: https://codereview.webrtc.org/1588693002 Cr-Commit-Position: refs/heads/master@{#11241}