Add tests for Element#elements.

client/html/generated/src/wrapping/_StyleSheetListWrappingImplementation.dart

 // Copyright (c) 2011, 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.
 
 // WARNING: Do not edit - generated code.
 
 class StyleSheetListWrappingImplementation extends DOMWrapperBase implements StyleSheetList {
   StyleSheetListWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
   int get length() { return _ptr.length; }
@@ skipping 20 matching lines @@
 
   void sort(int compare(StyleSheet a, StyleSheet b)) {
     throw new UnsupportedOperationException("Cannot sort immutable List.");
   }
 
   void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
     throw new UnsupportedOperationException("This object is immutable.");
   }
 
   int indexOf(StyleSheet element, [int start = 0]) {
-    return _Lists.indexOf(this, element, start, this.length);
+    return Lists.indexOf(this, element, start, this.length);
   }
 
   int lastIndexOf(StyleSheet element, [int start = null]) {
     if (start === null) start = length - 1;
-    return _Lists.lastIndexOf(this, element, start);
+    return Lists.lastIndexOf(this, element, start);
   }
 
   int clear() {
     throw new UnsupportedOperationException("Cannot clear immutable List.");
   }
 
   StyleSheet removeLast() {
     throw new UnsupportedOperationException("Cannot removeLast on immutable List.");
   }
 
@@ skipping 42 matching lines @@
   }
 
   Iterator<StyleSheet> iterator() {
     return new _FixedSizeListIterator<StyleSheet>(this);
   }
 
   StyleSheet item(int index) {
     return LevelDom.wrapStyleSheet(_ptr.item(index));
   }
 }