Remove unused ALLOCATE_DELAY constant.

Breaks linux_tsan2 compile [-Wunused-const-variable].

TBR=mallinath@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/20749004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6505 4adac7df-926f-26a2-2b94-8c16560cd09d