Speeding up ElementList.clear & NodeList.clear.

tools/dom/templates/html/impl/impl_Node.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;
 
 /**
  * Lazy implementation of the child nodes of an element that does not request
  * the actual child nodes of an element until strictly necessary greatly
  * improving performance for the typical cases where it is not required.
@@ skipping 120 matching lines @@
 
   void removeWhere(bool test(Node node)) {
     _filter(test, true);
   }
 
   void retainWhere(bool test(Node node)) {
     _filter(test, false);
   }
 
   void clear() {
-    _this.text = '';
+    _this._clearChildren();
   }
 
   void operator []=(int index, Node value) {
     _this._replaceChild(value, this[index]);
   }
 
   Iterator<Node> get iterator => _this.childNodes.iterator;
 
   // From List<Node>:
 
@@ skipping 100 matching lines @@
       for (var i = 0, len = otherList.length; i < len; ++i) {
         this.insertBefore(otherList._this.firstChild, refChild);
       }
     } else {
       for (var node in newNodes) {
         this.insertBefore(node, refChild);
       }
     }
   }
 
+  void _clearChildren() {
+    while (firstChild != null) {
+      _removeChild(firstChild);
+    }
+  }
+
   /**
    * Print out a String representation of this Node.
    */
   String toString() => nodeValue == null ? super.toString() : nodeValue;
 $!MEMBERS
 }