Make it easier and more efficient to use trusted HTML text

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 996 matching lines @@
    *     var createdElement = document.body.children[0];
    *     print(createdElement.classes[0]); // Prints 'something'
    *
    * See also:
    *
    * * [insertAdjacentText]
    * * [insertAdjacentElement]
    */
   void insertAdjacentHtml(String where, String html, {NodeValidator validator,
       NodeTreeSanitizer treeSanitizer}) {
-      _insertAdjacentNode(where, new DocumentFragment.html(html,
-          validator: validator, treeSanitizer: treeSanitizer));
+      if (treeSanitizer is _TrustedHtmlTreeSanitizer) {
+        _insertAdjacentHtml(where, html);
+      } else {
+        _insertAdjacentNode(where, new DocumentFragment.html(html,
+            validator: validator, treeSanitizer: treeSanitizer));
+      }
   }
 
 $if DART2JS
 
   @JSName('insertAdjacentHTML')
   void _insertAdjacentHtml(String where, String text) native;
 
   /**
    * Inserts [element] into the DOM at the specified location.
    *
@@ skipping 338 matching lines @@
    * are allowed by the provided validator.
    *
    * See also:
    *
    * * [NodeValidator]
    * * [NodeTreeSanitizer]
    */
   void setInnerHtml(String html,
     {NodeValidator validator, NodeTreeSanitizer treeSanitizer}) {
     text = null;
-    append(createFragment(
-        html, validator: validator, treeSanitizer: treeSanitizer));
+    if (treeSanitizer is _TrustedHtmlTreeSanitizer) {
+      _innerHtml = html;
+    } else {
+      append(createFragment(
+          html, validator: validator, treeSanitizer: treeSanitizer));
+    }
   }
   String get innerHtml => _innerHtml;
 
   /**
    * This is an ease-of-use accessor for event streams which should only be
    * used when an explicit accessor is not available.
    */
   ElementEvents get on => new ElementEvents(this);
   
   /**
@@ skipping 185 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');
 }