Remove function names on function expressions.

tests/compiler/dart2js_extra/closure2_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";
 
 closure0() {
   // A closure will be implemented as a class. Make sure everything is set up
   // correctly when no other class is generated. In particular we need
   // the Dart-Object class to be generated.
-  var f = fun() => 42;
+  var f = () => 42;
   Expect.equals(42, f());
 }
 
 main() {
   closure0();
 }