console.error when using unknown attributes in templates.

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.
 -->
 <import src="sky-binder.sky" as="binder" />
 <script>
 var templates = new Map();
 
 var attributeConverters = {
@@ skipping 22 matching lines @@
     },
     enumerable: true,
     configurable: true,
   });
 
   prototype[name + 'AttributeChanged'] = function(oldValue, newValue) {
     this.notifyPropertyChanged(name, converter(oldValue), converter(newValue));
   };
 }
 
-function defineReflectedAttributes(elementClass, list) {
-  var attributeNames = (list || '').split(',');
+function defineReflectedAttributes(elementClass, tagName, list) {
+  var attributeTokens = (list || '').split(',');
+  var attributeNames = [];
   var prototype = elementClass.prototype;
 
-  for (var i = 0; i < attributeNames.length; ++i) {
-    var parts = attributeNames[i].split(':');
+  for (var i = 0; i < attributeTokens.length; ++i) {
+    var parts = attributeTokens[i].split(':');
     var name = parts[0].trim();
     var type = (parts[1] || '').trim();
     var converter = attributeConverters[type] || attributeConverters.string;
 
+    attributeNames.push(name);
     defineReflectedAttribute(prototype, converter, name);
   }
+
+  binder.registerElement(tagName, {
+    attributeNames: attributeNames,
+  });
 }
 
 class SkyElement extends HTMLElement {
 
   static register() {
     var wrapper = document.currentScript.parentNode;
 
     if (wrapper.localName !== 'sky-element')
       throw new Error('No <sky-element>.');
 
     var tagName = wrapper.getAttribute('name');
     if (!tagName)
       throw new Error('<sky-element> must have a name.');
 
     var template = wrapper.querySelector('template');
     if (template)
       templates.set(tagName, template);
 
-    defineReflectedAttributes(this, wrapper.getAttribute('attributes'));
+    defineReflectedAttributes(this, tagName,
+        wrapper.getAttribute('attributes'));
 
     return document.registerElement(tagName, {
       prototype: this.prototype,
     });
   }
 
   created() {
     // override
   }
 
@@ skipping 61 matching lines @@
       oldValue: oldValue,
     });
     var handler = this[name + 'Changed'];
     if (typeof handler == 'function')
       handler.call(this, oldValue, newValue);
   }
 };
 
 module.exports = SkyElement;
 </script>