of an empty handle in case of an exception.  This problem can break
C++ programs that are not interested in catching exceptions and just
want to propagate them out by testing for empty handles.

The issue is that exceptions are not rescheduled if they are
externally caught.  Externally caught exceptions have to be
rescheduled if there is a JavaScript frame on the way to the C++ frame
that holds the external handler.
Review URL: http://codereview.chromium.org/43070

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1487 ce2b1a6d-e550-0410-aec6-3dcde31c8c00