pkg/code_transformers: removed unused imports, require latest unittest

pkg/code_transformers/test/resolver_test.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 code_transformers.test.resolver_test;
 
 import 'dart:async';
-import 'dart:io' show File, Platform;
 
 import 'package:barback/barback.dart';
 import 'package:code_transformers/resolver.dart';
 import 'package:code_transformers/tests.dart';
-import 'package:path/path.dart' as path;
 import 'package:unittest/compact_vm_config.dart';
 import 'package:unittest/unittest.dart';
 
 main() {
   useCompactVMConfiguration();
   var entryPoint = new AssetId('a', 'web/main.dart');
   var resolvers = new Resolvers(testingDartSdkDirectory);
 
   Future validateResolver({Map<String, String> inputs, void validator(Resolver),
       List<String> messages: const[]}) {
@@ skipping 321 matching lines @@
     this.resolvers = resolvers;
   }
 
   Future<bool> isPrimary(Asset input) =>
       new Future.value(input.id == primary);
 
   applyResolver(Transform transform, Resolver resolver) {
     return validator(resolver);
   }
 }