[8] Please review fix for 7177144: [macosx] Drag and drop not working (regression in 7u6)

[Alexander Zuev]

Hello,

  please review my fix for CR 7177144: [macosx] Drag and drop not 
working (regression in 7u6)

  I still tink we shouldn't move the instanceof check to the earlier 
stage since this check may be costly
so it should not be performed unless other possibilities are ruled out 
by the less expensive checks.

Bug description is: 
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7177144
Webrev can be found here: 
http://cr.openjdk.java.net/~kizune/7177144/webrev.01

With best regards,
Alex