Fix a GC issue

src/heap.cc

Index: src/heap.cc
===================================================================
--- src/heap.cc	(revision 2735)
+++ src/heap.cc	(working copy)
@@ -2089,8 +2089,9 @@
     if (count > in_object_properties) {
       count = in_object_properties;
     }
-    DescriptorArray* descriptors = *Factory::NewDescriptorArray(count);
-    if (descriptors->IsFailure()) return descriptors;
+    Object* descriptors_obj = DescriptorArray::Allocate(count);
+    if (descriptors_obj->IsFailure()) return descriptors_obj;
+    DescriptorArray* descriptors = DescriptorArray::cast(descriptors_obj);
     for (int i = 0; i < count; i++) {
       String* name = fun->shared()->GetThisPropertyAssignmentName(i);
       ASSERT(name->IsSymbol());