fix sky element

sky/framework/sky-element/sky-element.sky

 <!--
 // 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.
 -->
 <link rel="import" href="TemplateBinding.sky" />
 <script>
-var Base = Object.create(HTMLElement.prototype, {
+var Base = {
+  __proto__: HTMLElement.prototype,
+
   register: function() {
     // |this| is prototype
     var template = document.currentScript.previousElementSibling;
     if (template && template.localName == 'template')
       this.template_ = template;
   },
 
   createdCallback: function() {
   },
 
@@ skipping 15 matching lines @@
     // override
   },
 
   attributeChangedCallback: function(attrName, oldValue, newValue) {
     // reserved for canonical behavior
     this.attributeChanged(attrName, oldValue, newValue);
   },
 
   attributeChanged: function(attrName, oldValue, newValue) {
     // override
-  },
+  }
 };
 
 function SkyElement(prototype) {
   prototype.__proto__ = Base;
   document.registerElement(prototype.name, { prototype: prototype });
   prototype.register();
 };
 
 module.exports = SkyElement;
 </script>