[dart:html] rename custom elements callbacks to match spec

tools/dom/templates/html/impl/impl_Element.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 class _ChildrenElementList extends ListBase<Element>
     implements NodeListWrapper {
   // Raw Element.
   final Element _element;
@@ skipping 720 matching lines @@
    * The tag should be a valid HTML tag name.
    */
   static bool isTagSupported(String tag) {
     var e = _ElementFactoryProvider.createElement_tag(tag, null);
     return e is Element && !(e is UnknownElement);
   }
 
   /**
    * Called by the DOM when this element has been inserted into the live
    * document.
+   *
+   * More information can be found in the
+   * [Custom Elements](http://w3c.github.io/webcomponents/spec/custom/#dfn-attached-callback)
+   * draft specification.
    */
   @Experimental()
-  void enteredView() {}
+  void attached() {
+    // For the deprecation period, call the old callback.
+    enteredView();
+  }
 
   /**
    * Called by the DOM when this element has been removed from the live
    * document.
+   *
+   * More information can be found in the
+   * [Custom Elements](http://w3c.github.io/webcomponents/spec/custom/#dfn-detached-callback)
+   * draft specification.
    */
   @Experimental()
+  void detached() {
+    // For the deprecation period, call the old callback.
+    leftView();
+  }
+
+  /** *Deprecated*: override [attached] instead. */
+  @Experimental()
+  @deprecated
+  void enteredView() {}
+
+  /** *Deprecated*: override [detached] instead. */
+  @Experimental()
+  @deprecated
   void leftView() {}
 
   /**
    * Called by the DOM whenever an attribute on this has been changed.
    */
   void attributeChanged(String name, String oldValue, String newValue) {}
 
   // Hooks to support custom WebComponents.
 
 $if DART2JS
@@ skipping 579 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }