Some minor fixes.

pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.ir_nodes_sexpr;
 
 import '../constants/values.dart';
 import '../util/util.dart';
 import 'cps_ir_nodes.dart';
 
@@ skipping 335 matching lines @@
   String nameParameter(Parameter parameter) {
     assert(!_names.containsKey(parameter));
     return _names[parameter] = parameter.hint.name;
   }
 
   String nameClosureVariable(ClosureVariable variable) {
     assert(!_names.containsKey(variable));
     return _names[variable] = variable.hint.name;
   }
 
-  String nameClosureVariableIfAbsent(ClosureVariable variable) {
+  void nameClosureVariableIfAbsent(ClosureVariable variable) {
     if (!_names.containsKey(variable)) {
       _names[variable] = variable.hint.name;
     }
   }
 
   String nameContinuation(Continuation node) {
     assert(!_names.containsKey(node));
     return _names[node] = 'k${_continuationCounter++}';
   }
 
   String nameValue(Primitive node) {
     assert(!_names.containsKey(node));
     return _names[node] = 'v${_valueCounter++}';
   }
 
   void setReturnContinuation(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     _names[node] = 'return';
   }
 
   String getName(Node node) {
     assert(_names.containsKey(node));
     return _names[node];
   }
 }