Hiding FilteredElementList class and fixing FilteredElementList.length.

tests/html/svgelement_test.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.
 
 library SvgElementTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 import 'dart:svg' as svg;
 
@@ skipping 168 matching lines @@
   group('elementget', () {
     test('get', () {
       final el = new svg.SvgElement.svg("""
 <svg version="1.1">
   <circle></circle>
   <path></path>
   text
 </svg>""");
       expect(_nodeStrings(el.children), ["circle", "path"]);
     });
+
+    test('resize', () {
+      var el = new svg.SvgSvgElement();
+      var items = [new svg.CircleElement(), new svg.RectElement()];
+      el.children = items;
+      expect(el.children.length, 2);
+      el.children.length = 1;
+      expect(el.children.length, 1);
+      expect(el.children.contains(items[0]), true);
+      expect(el.children.contains(items[1]), false);
+
+      el.children.length = 0;
+      expect(el.children.contains(items[0]), false);
+    });
   });
 
   group('elementset', () {
     test('set', () {
       final el = new svg.SvgSvgElement();
       el.children = [new svg.SvgElement.tag("circle"), new svg.SvgElement.tag("path")];
       expect(el.innerHtml, '<circle></circle><path></path>');
     });
   });
 
   group('css', () {
     test('classes', () {
       var el = new svg.CircleElement();
       var classes = el.classes;
       expect(el.classes.length, 0);
       classes.toggle('foo');
       expect(el.classes.length, 1);
       classes.toggle('foo');
       expect(el.classes.length, 0);
     });
   });
 }