Clean-up imports

pkg/analyzer/example/resolver_driver.dart

 #!/usr/bin/env dart
 // Copyright (c) 2013, 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 'dart:io';
 
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/sdk.dart' show DartSdk;
 import 'package:analyzer/src/generated/sdk_io.dart' show DirectoryBasedDartSdk;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 
 void main(List<String> args) {
   print('working dir ${new File('.').resolveSymbolicLinksSync()}');
 
@@ skipping 47 matching lines @@
           var fullName =
               element.library.definingCompilationUnit.source.fullName;
           lines.add("  from $fullName");
         }
       }
     }
     print(lines.join('\n'));
     return super.visitNode(node);
   }
 }