Make arguments of MutationObserver named.

tests/html/mutationobserver_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('mutationobserver_test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 /**
@@ skipping 31 matching lines @@
         expect(() { mutationObserver.observe(document, {}); },
                throws);
       });
 
     test('direct-parallel options-map', () {
         var container = new DivElement();
         var div1 = new DivElement();
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
-        mutationObserver.observe(container, {'childList': true});
+        mutationObserver.observe(container, options: {'childList': true});
 
         container.nodes.add(div1);
         container.nodes.add(div2);
       });
 
     test('direct-parallel options-named', () {
         var container = new DivElement();
         var div1 = new DivElement();
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
-        // OPTIONALS mutationObserver.observe(container, childList: true);
-        mutationObserver.observe(container, {}, true);
+        mutationObserver.observe(container, childList: true);
 
         container.nodes.add(div1);
         container.nodes.add(div2);
       });
 
     test('direct-nested options-named', () {
         var container = new DivElement();
         var div1 = new DivElement();
         var div2 = new DivElement();
         var mutationObserver =
             new MutationObserver(mutationCallback(1, orderedEquals([div1])));
-        // OPTIONALS mutationObserver.observe(container, childList: true);
-        mutationObserver.observe(container, {}, true);
+        mutationObserver.observe(container, childList: true);
 
         container.nodes.add(div1);
         div1.nodes.add(div2);
       });
 
 
     test('subtree options-map', () {
         var container = new DivElement();
         var div1 = new DivElement();
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
         mutationObserver.observe(container,
-                                 {'childList': true, 'subtree': true});
+                                 options: {'childList': true, 'subtree': true});
 
         container.nodes.add(div1);
         div1.nodes.add(div2);
       });
 
     test('subtree options-named', () {
         var container = new DivElement();
         var div1 = new DivElement();
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
-        // OPTIONALS mutationObserver.observe(container, childList: true, subtree: true);
-        mutationObserver.observe(container, {}, true, null, null, true);
+        mutationObserver.observe(container, childList: true, subtree: true);
 
         container.nodes.add(div1);
         div1.nodes.add(div2);
       });
   });
 }