Make pub strong-mode clean.

test/dependency_computer/utils.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.
 
 import 'package:barback/barback.dart';
+import 'package:collection/collection.dart';
 import 'package:path/path.dart' as p;
+import 'package:scheduled_test/scheduled_test.dart';
+
 import 'package:pub/src/barback/cycle_exception.dart';
 import 'package:pub/src/barback/dependency_computer.dart';
 import 'package:pub/src/entrypoint.dart';
 import 'package:pub/src/io.dart';
 import 'package:pub/src/package.dart';
 import 'package:pub/src/package_graph.dart';
 import 'package:pub/src/system_cache.dart';
 import 'package:pub/src/utils.dart';
-import 'package:scheduled_test/scheduled_test.dart';
 
 import '../test_pub.dart';
 
 /// Expects that [DependencyComputer.transformersNeededByTransformers] will
 /// return a graph matching [expected] when run on the package graph defined by
 /// packages in the sandbox.
 void expectDependencies(Map<String, Iterable<String>> expected) {
   expected = mapMap(expected, value: (_, ids) => ids.toSet());
 
   schedule(() {
@@ skipping 89 matching lines @@
 
   buffer.writeln("""
 NoOpTransformer extends Transformer {
   bool isPrimary(AssetId id) => true;
   void apply(Transform transform) {}
 }
 """);
 
   return buffer.toString();
 }