Add proper support for proxies to HType.

test/mjsunit/regress/regress-crbug-448730.js

+// Copyright 2015 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 --harmony-proxies
+
+function bar() {}
+bar({ a: Proxy.create({}) });
+function foo(x) { x.a.b == ""; }
+var x = {a: {b: "" }};
+foo(x);
+foo(x);
+%OptimizeFunctionOnNextCall(foo);
+foo(x);