Add an UNUSED_SHOWN_NAMES hint to the analyzer

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, 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 analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 2746 matching lines @@
     // Generate errors.
     //
     unit.accept(new DeadCodeVerifier(errorReporter, typeSystem: typeSystem));
     // Verify imports.
     {
       ImportsVerifier verifier = new ImportsVerifier();
       verifier.addImports(unit);
       usedImportedElementsList.forEach(verifier.removeUsedElements);
       verifier.generateDuplicateImportHints(errorReporter);
       verifier.generateUnusedImportHints(errorReporter);
+      verifier.generateUnusedShownNameHints(errorReporter);
     }
     // Unused local elements.
     {
       UsedLocalElements usedElements =
           new UsedLocalElements.merge(usedLocalElementsList);
       UnusedLocalElementsVerifier visitor =
           new UnusedLocalElementsVerifier(errorListener, usedElements);
       unitElement.accept(visitor);
     }
     // Dart2js analysis.
@@ skipping 2712 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }