pkg/compiler: fix imports

pkg/compiler/lib/src/elements/visitor.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.
 
 library visitor;
 
-import 'elements.dart';
 import '../closure.dart'
     show BoxFieldElement, ClosureClassElement, ClosureFieldElement;
+import 'elements.dart';
 
 abstract class ElementVisitor<R, A> {
   const ElementVisitor();
 
   R visit(Element e, A arg) => e.accept(this, arg);
 
   R visitErroneousElement(ErroneousElement e, A arg) => null;
   R visitWarnOnUseElement(WarnOnUseElement e, A arg) => null;
   R visitAmbiguousElement(AmbiguousElement e, A arg) => null;
   R visitCompilationUnitElement(CompilationUnitElement e, A arg) => null;
@@ skipping 177 matching lines @@
   @override
   R visitClosureClassElement(ClosureClassElement e, A arg) {
     return visitClassElement(e, arg);
   }
 
   @override
   R visitClosureFieldElement(ClosureFieldElement e, A arg) {
     return visitVariableElement(e, arg);
   }
 }