Attempt no. 3 to fix Heap::IsHeapIterable and HeapIterator

test/mjsunit/regress/regress-373283.js

Index: test/mjsunit/regress/regress-373283.js
diff --git a/test/mjsunit/regress/regress-373283.js b/test/mjsunit/regress/regress-373283.js
new file mode 100644
index 0000000000000000000000000000000000000000..20cee4d808ed681786503ea9e2c5f876daadd63d
--- /dev/null
+++ b/test/mjsunit/regress/regress-373283.js
@@ -0,0 +1,18 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags:  --allow-natives-syntax --deopt-every-n-times=1
+
+function __f_0() {
+  var x = [];
+  x[21] = 1;
+  x[21] + 0;
+}
+
+for (var i = 0; i < 3; i++) __f_0();
+%OptimizeFunctionOnNextCall(__f_0);
+for (var i = 0; i < 10; i++) __f_0();
+%OptimizeFunctionOnNextCall(__f_0);
+__f_0();
+%GetScript("foo");