Added missing include to os2.cc. 

os2.cc uses stddef.h's offsetof().

Original review: http://codereview.chromium.org/7113013/

git-svn-id: http://ots.googlecode.com/svn/trunk@69 a4e77c2c-9104-11de-800e-5b313e0d2bf3
1 file changed