Avoid mangling the name of native methods.

frog/gen.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.
 
 /**
  * Top level generator object for writing code and keeping track of
  * dependencies.
  *
  * Should have two compilation models, but only one implemented so far.
  *
@@ skipping 1269 matching lines @@
     }
 
     // We're done! Write the final code.
     savedWriter.write(writer.text);
     writer = savedWriter;
     savedCounters.add(counters);
     counters = savedCounters;
   }
 
   MethodMember _makeLambdaMethod(String name, FunctionDefinition func) {
-    var meth = new MethodMember(name, method.declaringType, func);
-    meth.isLambda = true;
+    var meth = new MethodMember.lambda(name, method.declaringType, func);
     meth.enclosingElement = method;
     meth._methodData = new MethodData(meth, this);
     meth.resolve();
     return meth;
   }
 
   visitBool(Expression node) {
     // Boolean conversions in if/while/do/for/conditions require non-null bool.
 
     // TODO(jmesserly): why do we have this rule? It seems inconsistent with
@@ skipping 1148 matching lines @@
     return true;
   }
 
 }
 
 class ReturnKind {
   static final int IGNORE = 1;
   static final int POST = 2;
   static final int PRE = 3;
 }