Avoid mangling the name of native methods.

frog/type.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.
 
 class Type extends Element {
   bool isTested = false;
   bool isChecked = false;
   bool isWritten = false;
 
   /**
@@ skipping 894 matching lines @@
     members[methodName] = method;
   }
 
   addField(VariableDefinition definition) {
     for (int i=0; i < definition.names.length; i++) {
       var name = definition.names[i].name;
       if (members.containsKey(name)) {
         world.error('duplicate field definition of "$name"',
           definition.span);
         return;