[WIP] bindings: Introduce PropertyBag

Source/core/dom/DOMPoint.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/DOMPoint.h"
 
 namespace blink {
 
 DOMPoint* DOMPoint::create(const Dictionary& point)
 {
     double x = 0;
     double y = 0;
     double z = 0;
     double w = 0;
 
-    if (!DictionaryHelper::get(point, "x", x))
+    if (!point.get("x", x))
         x = 0;
-    if (!DictionaryHelper::get(point, "y", y))
+    if (!point.get("y", y))
         y = 0;
-    if (!DictionaryHelper::get(point, "z", z))
+    if (!point.get("z", z))
         z = 0;
-    if (!DictionaryHelper::get(point, "w", w))
+    if (!point.get("w", w))
         w = 1;
 
     return new DOMPoint(x, y, z, w);
 }
 
 DOMPoint* DOMPoint::create(double x, double y, double z, double w)
 {
     return new DOMPoint(x, y, z, w);
 }
 
 DOMPoint::DOMPoint(double x, double y, double z, double w)
     : DOMPointReadOnly(x, y, z, w)
 {
 }
 
 } // namespace blink