Adds missing include of assert header.

BUG=3380
R=sergeyu@chromium.org

Review URL: https://webrtc-codereview.appspot.com/14569008

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6221 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed