dart2js: Fix hints in code base.

pkg/compiler/lib/src/native/enqueue.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.
 
 part of native;
 
 /**
  * This could be an abstract class but we use it as a stub for the dart_backend.
  */
 class NativeEnqueuer {
@@ skipping 156 matching lines @@
     //
     //     class B extends foo.A {}
     //
     // String "A" has a potential subclass B.
 
     var potentialExtends = new Map<String, Set<ClassElement>>();
 
     libraries.forEach((library) {
       library.implementation.forEachLocalMember((element) {
         if (element.isClass) {
-          String name = element.name;
           String extendsName = findExtendsNameOfClass(element);
           if (extendsName != null) {
             Set<ClassElement> potentialSubclasses =
                 potentialExtends.putIfAbsent(
                     extendsName,
                     () => new Set<ClassElement>());
             potentialSubclasses.add(element);
           }
         }
       });
@@ skipping 501 matching lines @@
         superclass,
         () => <ClassElement>[]);
     directSubtypes.add(cls);
   }
 
   void logSummary(log(message)) {
     log('Compiled ${registeredClasses.length} native classes, '
         '${unusedClasses.length} native classes omitted.');
   }
 }