Removing dart:html APIs which were deprecated in M2.

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 html;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 549 matching lines @@
 
   void set attributes(Map<String, String> value) {
     Map<String, String> attributes = this.attributes;
     attributes.clear();
     for (String key in value.keys) {
       attributes[key] = value[key];
     }
   }
 
   /**
-   * Deprecated, use innerHtml instead.
-   */
-  @deprecated
-  String get innerHTML => this.innerHtml;
-  @deprecated
-  void set innerHTML(String value) {
-    this.innerHtml = value;
-  }
-
-  @deprecated
-  void set elements(Collection<Element> value) {
-    this.children = value;
-  }
-
-  /**
-   * Deprecated, use [children] instead.
-   */
-  @deprecated
-  List<Element> get elements => this.children;
-
-  /**
    * List of the direct children of this element.
    *
    * This collection can be used to add and remove elements from the document.
    *
    *     var item = new DivElement();
    *     item.text = 'Something';
    *     document.body.children.add(item) // Item is now displayed on the page.
    *     for (var element in document.body.children) {
    *       element.style.background = 'red'; // Turns every child of body red.
    *     }
@@ skipping 439 matching lines @@
 $if DART2JS
   // Optimization to improve performance until the dart2js compiler inlines this
   // method.
   static dynamic createElement_tag(String tag) =>
       JS('Element', 'document.createElement(#)', tag);
 $else
   static Element createElement_tag(String tag) =>
       document.$dom_createElement(tag);
 $endif
 }