Fix exception propagation problem where undefined was returned instead...

Fix exception propagation problem where undefined was returned instead
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.

Committed: http://code.google.com/p/v8/source/detail?r=1487

[Søren Thygesen Gjesse, 2009-03-11 10:44:18]

LGTM

Maybe extend the ExceptionOrder test in test-api, as it should have caught this.

http://codereview.chromium.org/43070/diff/1/4
File src/top.h (right):

http://codereview.chromium.org/43070/diff/1/4#newcode161
Line 161: if (!thread_local_.external_caught_exception_) {
Is this if just to avoid recalculation, or is there a subtle reason for it? Good
to get rid of IsTheHole in here.

[Christian Plesner Hansen, 2009-03-11 10:53:35]

Lgtm

[Mads Ager (chromium), 2009-03-11 11:09:52]

http://codereview.chromium.org/43070/diff/1/4
File src/top.h (right):

http://codereview.chromium.org/43070/diff/1/4#newcode161
Line 161: if (!thread_local_.external_caught_exception_) {
The external_caught_exception flag has to be sticky while propagating the
exception out.  It will be explicitly cleared when it is OK to do so.