Fix detached callback and add isAttached to SkyElements.

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="TemplateBinding.sky" />
 <script>
 var templates = new Map();
 
+var kInternal = Symbol("SkyElementInternal");

[rafaelw, 2014/12/19 23:22:56]

nit: let's not use this kind of naming. How about 'internalSymbol'?

+
+class Internal {
+  constructor() {
+    this.appendedTemplate = false;
+    this.isAttached = false;
+  }
+};
+
 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);
 
     return document.registerElement(tagName, {
       prototype: this.prototype,
     });
   }
 
   created() {
     // override
   }
 
   attached() {
     // override
   }
 
-  dettached() {
+  detached() {
     // override
   }
 
   attributeChanged(attrName, oldValue, newValue) {
     // override
   }
 
   shadowRootReady() {
     // override
   }
 
   createdCallback() {
+    this[kInternal] = new Internal();
     this.created();
   }
 
+  get isAttached() {
+    return this[kInternal].isAttached;
+  }
+
   attachedCallback() {
-    if (!this.shadowRoot) {
+    var internal = this[kInternal];
+
+    if (!internal.appendedTemplate) {
       var template = templates.get(this.localName);
       if (template) {
         var shadow = this.ensureShadowRoot();
         shadow.appendChild(template.createInstance(this));
         this.shadowRootReady();
+        internal.appendedTemplate = true;
       }
     }
+
     this.attached();
+    internal.isAttached = true;
   }
 
-  dettachedCallback() {
-    this.dettached();
+  detachedCallback() {
+    this.detached();
+    this[kInternal].isAttached = false;
   }
 
   attributeChangedCallback(attrName, oldValue, newValue) {
     // reserved for canonical behavior
     this.attributeChanged(attrName, oldValue, newValue);
   }
 };
 
 module.exports = SkyElement;
 </script>