Fix the exception order by remember JS handler in an external handler.

src/api.cc

Index: src/api.cc
===================================================================
--- src/api.cc	(revision 742)
+++ src/api.cc	(working copy)
@@ -1081,7 +1081,8 @@
       exception_(i::Heap::the_hole_value()),
       message_(i::Smi::FromInt(0)),
       is_verbose_(false),
-      capture_message_(true) {
+      capture_message_(true),
+      js_handler_(NULL) {
   i::Top::RegisterTryCatchHandler(this);
 }