Storing raw audio sink for default audio track.
Storing raw audio sink for default audio track.

BUG=webrtc:5250

Committed: https://crrev.com/e591f9377f33f3f725a30faecd1bef1a71fa6b99
Cr-Commit-Position: refs/heads/master@{#11230}

Review URL: https://codereview.webrtc.org/1551813002

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11275}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 884f58523a75ace3239805759147948b7e868aea

jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk