Fire 'stack' getter of error objects after GC.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index de47c94a8a4a59f4ad5224ed209c3145fa990563..e5f290086fe06920ecf13598d115b57652641d0d 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -644,6 +644,19 @@ void ExternalStringTable::ShrinkNewStrings(int position) {
 }
 
 
+void ErrorObjectList::Add(JSObject* object) {
+  list_.Add(object);
+}
+
+
+void ErrorObjectList::Iterate(ObjectVisitor* v) {
+  if (!list_.is_empty()) {
+    Object** start = &list_[0];
+    v->VisitPointers(start, start + list_.length());
+  }
+}
+
+
 void Heap::ClearInstanceofCache() {
   set_instanceof_cache_function(the_hole_value());
 }