Make 'where' lazy.

tests/html/node_test.dart

Index: tests/html/node_test.dart
diff --git a/tests/html/node_test.dart b/tests/html/node_test.dart
index 10b914beb86edc31d20d1e3e2c4cf38018cc4d8d..42c4bd27698a7ee8c03970d541e619545ccf10a7 100644
--- a/tests/html/node_test.dart
+++ b/tests/html/node_test.dart
@@ -79,8 +79,9 @@ main() {
       expect(nodes[2], isComment);
     });
 
-    test('filter', () {
-      var filtered = makeNodeWithChildren().nodes.where((n) => n is BRElement);
+    test('where', () {
+      var filtered =
+          makeNodeWithChildren().nodes.where((n) => n is BRElement).toList();
       expect(filtered.length, 1);
       expect(filtered[0], isBRElement);
       expect(filtered, isNodeList);
@@ -183,15 +184,15 @@ main() {
 
   group('_NodeList', () {
     List<Node> makeNodeList() =>
-      makeNodeWithChildren().nodes.where((_) => true);
+      makeNodeWithChildren().nodes.where((_) => true).toList();
 
     test('first', () {
       var nodes = makeNodeList();
       expect(nodes.first, isText);
     });
 
-    test('filter', () {
-      var filtered = makeNodeList().where((n) => n is BRElement);
+    test('where', () {
+      var filtered = makeNodeList().where((n) => n is BRElement).toList();
       expect(filtered.length, 1);
       expect(filtered[0], isBRElement);
       expect(filtered, isNodeList);