Update Function.apply to use Symbol.

dart/tests/corelib/apply2_test.dart

 // Copyright (c) 2012, 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.
 
 import "package:expect/expect.dart";
+import "symbol_map_helper.dart";
 
 apply(Function function, ArgumentDescriptor args) {
   return Function.apply(
-      function, args.positionalArguments, args.namedArguments);
+      function, args.positionalArguments,
+      symbolMapToStringMap(args.namedArguments));
 }
 
 class ArgumentDescriptor {
   final List positionalArguments;
   final Map<String, dynamic> namedArguments;
 
   ArgumentDescriptor(this.positionalArguments, this.namedArguments);
 }
 
 void throwsNSME(function) {
@@ skipping 59 matching lines @@
       apply(c6, new ArgumentDescriptor([], {'a': 3, 'b': 4})));
   Expect.equals('c6 4 3',
       apply(c6, new ArgumentDescriptor([], {'b': 3, 'a': 4})));
   Expect.equals('c6 2 3',
       apply(c6, new ArgumentDescriptor([], {'b': 3})));
   throwsNSME(() => apply(c6, new ArgumentDescriptor([1], {'a': 1})));
   throwsNSME(() => apply(c6, new ArgumentDescriptor([1], {})));
   throwsNSME(() =>
       apply(c6, new ArgumentDescriptor([], {'a': 1, 'b': 2, 'c': 3})));
 }