Ensure the constant operand for heap-object store-named-field is not a smi.

test/mjsunit/regress/regress-store-heapobject.js

 // 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
 
-function f() {
-  var o = {x:1};
-  var y = {y:2.5, x:0};
-  var result;
-  for (var i = 0; i < 2; i++) {
-    result = o.x + 3;
-    o = y;
-  }
-  return result;
+var o = {a: undefined};
+
+function store(o, v) {
+  o.a = v;
 }
 
-f();
-f();
+store(o, undefined);
+store(o, undefined);
+
+function f(bool) {
+  var o = {a: undefined};
+  if (bool) {
+    store(o, 1);
+  }
+  return o;
+}
+
+f(false);
+f(false);
 %OptimizeFunctionOnNextCall(f);
-assertEquals(3, f());
+f(true);