use symbol literals instead of const ctor in packages

pkg/polymer/lib/src/declaration.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.
 
 part of polymer;
 
 /**
  * **Deprecated**: use [Polymer.register] instead.
  *
  * Registers a [PolymerElement]. This is similar to [registerCustomElement]
@@ skipping 219 matching lines @@
     // compile list of attributes to copy to instances
     accumulateInstanceAttributes();
     // parse on-* delegates declared on `this` element
     parseHostEvents();
     // parse on-* delegates declared in templates
     parseLocalEvents();
     // install external stylesheets as if they are inline
     installSheets();
     // TODO(jmesserly): this feels unnatrual in Dart. Since we have convenient
     // lazy static initialization, can we get by without it?
-    var registered = type.methods[const Symbol('registerCallback')];
+    var registered = type.methods[#registerCallback];
     if (registered != null && registered.isStatic &&
         registered.isRegularMethod) {
-      type.invoke(const Symbol('registerCallback'), [this]);
+      type.invoke(#registerCallback, [this]);
     }
 
   }
 
   void registerType(String name) {
     // TODO(jmesserly): document.register
     registerCustomElement(name, () =>
         type.newInstance(const Symbol(''), const []).reflectee);
   }
 
@@ skipping 322 matching lines @@
   }
 
   return props;
 }
 
 bool _hasSetter(ClassMirror type, MethodMirror getter) {
   var setterName = new Symbol('${MirrorSystem.getName(getter.simpleName)}=');
   return type.setters.containsKey(setterName);
 }
 
-bool _inDartHtml(ClassMirror type) =>
-    type.owner.simpleName == const Symbol('dart.dom.html');
+bool _inDartHtml(ClassMirror type) => type.owner.simpleName == #dart.dom.html;
 
 
 /** Attribute prefix used for declarative event handlers. */
 const _EVENT_PREFIX = 'on-';
 
 /** Whether an attribute declares an event. */
 bool _hasEventPrefix(String attr) => attr.startsWith(_EVENT_PREFIX);
 
 String _removeEventPrefix(String name) => name.substring(_EVENT_PREFIX.length);
 
@@ skipping 106 matching lines @@
   return map;
 }();
 
 // Dart note: we need this function because we have additional renames JS does
 // not have. The JS renames are simply case differences, whereas we have ones
 // like doubleclick -> dblclick and stripping the webkit prefix.
 String _eventNameFromType(String eventType) {
   final result = _reverseEventTranslations[eventType];
   return result != null ? result : eventType;
 }