Fix a data race in ACM1 when audio is pulled.

BUG=chromium:348511
R=henrik.lundin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/13389004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6026 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed