Fix analyzer hints and warnings in test/.

test/transformer/cache_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
 
-import 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
-import '../serve/utils.dart';
 
 const REPLACE_FROM_LIBRARY_TRANSFORMER = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:bar/bar.dart';
 
 class ReplaceTransformer extends Transformer {
   ReplaceTransformer.asPlugin();
 
@@ skipping 314 matching lines @@
   Future apply(Transform transform) {
     return transform.primaryInput.readAsString().then((contents) {
       transform.addOutput(new Asset.fromString(
           transform.primaryInput.id,
           contents.replaceAll("$input", "$output")));
     });
   }
 }
 """;
 }