pkg: analysis aided cleanup

pkg/mutation_observer/test/mutation_observer_test.dart

 // Copyright (c) 2013, 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 mutation_observer_test;
 
 import 'dart:html';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
@@ skipping 44 matching lines @@
         }
       }
 
       return expectAsyncUntil2(callback, () => done);
     }
 
     test('empty options is syntax error', () {
       var mutationObserver = new MutationObserver(
           (mutations, observer) { expect(false, isTrue,
               reason: 'Should not be reached'); });
-      expect(() { mutationObserver.observe(document, {}); },
+      expect(() { mutationObserver.observe(document); },
              throws);
     });
 
     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])));
       mutationObserver.observe(container, childList: true);
@@ skipping 29 matching lines @@
     test('mutation event', () {
       var event = new MutationEvent('something', prevValue: 'prev',
           newValue: 'new', attrName: 'attr');
       expect(event is MutationEvent, isTrue);
       expect(event.prevValue, 'prev');
       expect(event.newValue, 'new');
       expect(event.attrName, 'attr');
     });
   });
 }