audio_processing_unittest: unbreak clang compilation.

BUG=2735
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/6069004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5313 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed