use symbol literals instead of const ctor in packages

pkg/mdv/test/custom_element_bindings_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 custom_element_bindings_test;
 
 import 'dart:html';
 import 'package:mdv/mdv.dart' as mdv;
 import 'package:unittest/html_config.dart';
 import 'package:unittest/unittest.dart';
 import 'mdv_test_utils.dart';
 
 main() {
   mdv.initialize();
   useHtmlConfiguration();
   group('Custom Element Bindings', customElementBindingsTest);
 }
 
-sym(x) => new Symbol(x);
-
 customElementBindingsTest() {
   var testDiv;
 
   setUp(() {
     document.body.append(testDiv = new DivElement());
   });
 
   tearDown(() {
     testDiv.remove();
     testDiv = null;
@@ skipping 15 matching lines @@
   observeTest('override bind/unbind/unbindAll', () {
     var element = new MyCustomElement();
     var model = toSymbolMap({'a': new Point(123, 444), 'b': new Monster(100)});
 
     element.bind('my-point', model, 'a');
     element.bind('scary-monster', model, 'b');
 
     expect(element.attributes, isNot(contains('my-point')));
     expect(element.attributes, isNot(contains('scary-monster')));
 
-    expect(element.myPoint, model[sym('a')]);
-    expect(element.scaryMonster, model[sym('b')]);
+    expect(element.myPoint, model[#a]);
+    expect(element.scaryMonster, model[#b]);
 
-    model[sym('a')] = null;
+    model[#a] = null;
     performMicrotaskCheckpoint();
     expect(element.myPoint, null);
     element.unbind('my-point');
 
-    model[sym('a')] = new Point(1, 2);
-    model[sym('b')] = new Monster(200);
+    model[#a] = new Point(1, 2);
+    model[#b] = new Monster(200);
     performMicrotaskCheckpoint();
-    expect(element.scaryMonster, model[sym('b')]);
+    expect(element.scaryMonster, model[#b]);
     expect(element.myPoint, null, reason: 'a was unbound');
 
     element.unbindAll();
-    model[sym('b')] = null;
+    model[#b] = null;
     performMicrotaskCheckpoint();
     expect(element.scaryMonster.health, 200);
   });
 
   observeTest('override attribute setter', () {
     var element = new WithAttrsCustomElement().real;
     var model = toSymbolMap({'a': 1, 'b': 2});
     element.bind('hidden?', model, 'a');
     element.bind('id', model, 'b');
 
     expect(element.attributes, contains('hidden'));
     expect(element.attributes['hidden'], '');
     expect(element.id, '2');
 
-    model[sym('a')] = null;
+    model[#a] = null;
     performMicrotaskCheckpoint();
     expect(element.attributes, isNot(contains('hidden')),
         reason: 'null is false-y');
 
-    model[sym('a')] = false;
+    model[#a] = false;
     performMicrotaskCheckpoint();
     expect(element.attributes, isNot(contains('hidden')));
 
-    model[sym('a')] = 'foo';
+    model[#a] = 'foo';
     // TODO(jmesserly): this is here to force an ordering between the two
     // changes. Otherwise the order depends on what order StreamController
     // chooses to fire the two listeners in.
     performMicrotaskCheckpoint();
 
-    model[sym('b')] = 'x';
+    model[#b] = 'x';
     performMicrotaskCheckpoint();
     expect(element.attributes, contains('hidden'));
     expect(element.attributes['hidden'], '');
     expect(element.id, 'x');
 
     expect(element.xtag.attributes.log, [
       ['remove', 'hidden?'],
       ['[]=', 'hidden', ''],
       ['[]=', 'id', '2'],
       ['remove', 'hidden'],
@@ skipping 20 matching lines @@
     mdv.instanceCreated.add(callback);
 
     div.query('template').model = model;
     performMicrotaskCheckpoint();
 
     var element = div.nodes[1];
 
     expect(element.xtag is MyCustomElement, true,
         reason: '${element.xtag} should be a MyCustomElement');
 
-    expect(element.xtag.myPoint, model[sym('a')]);
-    expect(element.xtag.scaryMonster, model[sym('b')]);
+    expect(element.xtag.myPoint, model[#a]);
+    expect(element.xtag.scaryMonster, model[#b]);
 
     expect(element.attributes, isNot(contains('my-point')));
     expect(element.attributes, isNot(contains('scary-monster')));
 
-    model[sym('a')] = null;
+    model[#a] = null;
     performMicrotaskCheckpoint();
     expect(element.xtag.myPoint, null);
 
     div.query('template').model = null;
     performMicrotaskCheckpoint();
 
     expect(element.parentNode, null, reason: 'element was detached');
 
-    model[sym('a')] = new Point(1, 2);
-    model[sym('b')] = new Monster(200);
+    model[#a] = new Point(1, 2);
+    model[#b] = new Monster(200);
     performMicrotaskCheckpoint();
 
     expect(element.xtag.myPoint, null, reason: 'model was unbound');
     expect(element.xtag.scaryMonster.health, 100, reason: 'model was unbound');
 
     mdv.instanceCreated.remove(callback);
   });
 
 }
 
@@ skipping 104 matching lines @@
   bool get isEmpty => _map.isEmpty;
   bool get isNotEmpty => _map.isNotEmpty;
 }
 
 /**
  * Sanitizer which does nothing.
  */
 class NullTreeSanitizer implements NodeTreeSanitizer {
   void sanitizeTree(Node node) {}
 }