Fix test after r21299.

This fixes Win and Mac test failures.

TBR=danno@chromium.org

Review URL: https://codereview.chromium.org/282863005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21303 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/cctest/test-heap.cc

@@ -3919,8 +3919,12 @@ TEST(NoWeakHashTableLeakWithIncrementalMarking) {
     }
     heap->CollectAllGarbage(i::Heap::kNoGCFlags);
   }
-  WeakHashTable* table = WeakHashTable::cast(heap->weak_object_to_code_table());
-  CHECK_EQ(0, table->NumberOfElements());
+  int elements = 0;
+  if (heap->weak_object_to_code_table()->IsHashTable()) {
+    WeakHashTable* t = WeakHashTable::cast(heap->weak_object_to_code_table());
+    elements = t->NumberOfElements();
+  }
+  CHECK_EQ(0, elements);
 }