Address Peter's comments on the new parameter specification implementation.

lib/compiler/implementation/js_backend/namer.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.
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer {
   final Compiler compiler;
 
@@ skipping 102 matching lines @@
     } else {
       StringBuffer suffix = new StringBuffer();
       signature.forEachOptionalParameter((Element element) {
         String jsName = JsNames.getValid(element.name.slowToString());        
         suffix.add('\$$jsName');
       });
       return '$methodName$suffix';
     }
   }
 
-  String instanceMethodNameByArity(SourceString name, int arity) {
+  String publicInstanceMethodNameByArity(SourceString name, int arity) {
+    assert(!name.isPrivate());
     return '${name.slowToString()}\$$arity';
   }
 
   String instanceMethodInvocationName(LibraryElement lib, SourceString name,
                                       Selector selector) {
     // TODO(floitsch): mangle, while preserving uniqueness.
     StringBuffer buffer = new StringBuffer();
     List<SourceString> names = selector.getOrderedNamedArguments();
     for (SourceString argumentName in names) {
       buffer.add(@'$');
@@ skipping 168 matching lines @@
   }
 
   String safeName(String name) {
     if (jsReserved.contains(name) || name.startsWith('\$')) {
       name = "\$$name";
       assert(!jsReserved.contains(name));
     }
     return name;
   }
 }