Make mappedBy lazy.

tests/html/xmlelement_test.dart

 // 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.
 
 library XMLElementTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
@@ skipping 39 matching lines @@
       final el = new XMLElement.tag('foo');
       expect(el, isXMLElement);
       expect(el.tagName, 'foo');
     });
   });
 
   // FilteredElementList is tested more thoroughly in DocumentFragmentTests.
   group('elements', () {
     test('filters out non-element nodes', () {
       final el = new XMLElement.xml("<xml>1<a/><b/>2<c/>3<d/></xml>");
-      expect(el.elements.mappedBy((e) => e.tagName), ["a", "b", "c", "d"]);
+      expect(el.elements.mappedBy((e) => e.tagName).toList(),
+             ["a", "b", "c", "d"]);
     });
 
     test('overwrites nodes when set', () {
       final el = new XMLElement.xml("<xml>1<a/><b/>2<c/>3<d/></xml>");
       el.elements = [new XMLElement.tag('x'), new XMLElement.tag('y')];
       expect(el.outerHTML, "<xml><x></x><y></y></xml>");
     });
   });
 
   group('classes', () {
@@ skipping 37 matching lines @@
 
     test('iterator', () {
       final classes = <String>[];
       for (var el in makeClassSet()) {
         classes.add(el);
       }
       expect(classes, unorderedEquals(['foo', 'bar', 'baz']));
     });
 
     test('map', () {
-      expect(makeClassSet().mappedBy((c) => c.toUpperCase()),
+      expect(makeClassSet().mappedBy((c) => c.toUpperCase()).toList(),
           unorderedEquals(['FOO', 'BAR', 'BAZ']));
     });
 
     test('filter', () {
       expect(makeClassSet().where((c) => c.contains('a')),
           unorderedEquals(['bar', 'baz']));
     });
 
     test('every', () {
       expect(makeClassSet().every((c) => c is String), isTrue);
@@ skipping 281 matching lines @@
 
   test('query', () {
     final el = makeElement();
     expect(el.query('foo').tagName, 'foo');
     expect(el.query('baz'), isNull);
   });
 
   test('queryAll', () {
     final el = new XMLElement.xml(
         "<xml><foo id='f1' /><bar><foo id='f2' /></bar></xml>");
-    expect(el.queryAll('foo').mappedBy((e) => e.id), ['f1', 'f2']);
+    expect(el.queryAll('foo').mappedBy((e) => e.id).toList(), ['f1', 'f2']);
     expect(el.queryAll('baz'), []);
   });
 
   // TODO(nweiz): re-enable this when matchesSelector works cross-browser.
   //
   // test('matchesSelector', () {
   //   final el = makeElement();
   //   expect(el.matchesSelector('*'), isTrue);
   //   expect(el.matchesSelector('xml'), isTrue);
   //   expect(el.matchesSelector('html'), isFalse);
@@ skipping 141 matching lines @@
     makeElement().rect.then(
       expectAsync1(ElementRect rect) {
         expectEmptyRect(rect.client);
         expectEmptyRect(rect.offset);
         expectEmptyRect(rect.scroll);
         expectEmptyRect(rect.bounding);
         expect(rect.clientRects.isEmpty, isTrue);
       }));
   });
 }