numAppContexts is accessed in non-threadsafe way in sun.awt.AppContext

FULL PRODUCT VERSION :
jdk7b147

A DESCRIPTION OF THE PROBLEM :
The numAppContexts variable, which is used to count the number of active AppContexts is used in a non-threadsafe way, as read-modify-write operators are not thread-safe on volatile fields.

I plan to submit a fix via OpenJDK, so I just need a bug-id ;)


REPRODUCIBILITY :
This bug can be reproduced always.