Don't use LOG() in callback.h

Because chromium is compiled with a different version of logging macros
defined in logging.h that header cannot be used in headers that can
also included from chromium code. Removed LOG_F(LS_WARNING) from
callback.h . That issue would block this code from being rolled in
chromium.

R=mallinath@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/8279004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/talk@5507 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed