Make pub strong-mode clean.

test/descriptor.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.
 
 /// Pub-specific scheduled_test descriptors.
 import 'package:oauth2/oauth2.dart' as oauth2;
 import 'package:pub/src/io.dart';
 import 'package:pub/src/utils.dart';
 import 'package:scheduled_test/descriptor.dart';
 import 'package:scheduled_test/scheduled_server.dart';
@@ skipping 38 matching lines @@
 /// [contents] may contain [Future]s that resolve to serializable objects,
 /// which may in turn contain [Future]s recursively.
 Descriptor pubspec(Map contents) {
   return async(awaitObject(contents).then((resolvedContents) =>
       file("pubspec.yaml", yaml(resolvedContents))));
 }
 
 /// Describes a file named `pubspec.yaml` for an application package with the
 /// given [dependencies].
 Descriptor appPubspec([Map dependencies]) {
-  var map = {"name": "myapp"};
+  var map = <String, dynamic>{"name": "myapp"};
   if (dependencies != null) map["dependencies"] = dependencies;
   return pubspec(map);
 }
 
 /// Describes a file named `pubspec.yaml` for a library package with the given
 /// [name], [version], and [deps]. If "sdk" is given, then it adds an SDK
 /// constraint on that version.
 Descriptor libPubspec(String name, String version, {Map deps, String sdk}) {
   var map = packageMap(name, version, deps);
   if (sdk != null) map["environment"] = {"sdk": sdk};
@@ skipping 124 matching lines @@
 ///
 /// [dependencies] maps package names to strings describing where the packages
 /// are located on disk. If the strings are semantic versions, then the packages
 /// are located in the system cache; otherwise, the strings are interpreted as
 /// relative `file:` URLs.
 ///
 /// Validation checks that the `.packages` file exists, has the expected
 /// entries (one per key in [dependencies]), each with a path that contains
 /// either the version string (for a reference to the pub cache) or a
 /// path to a path dependency, relative to the application directory.
-Descriptor packagesFile([Map dependencies]) =>
+Descriptor packagesFile([Map<String, String> dependencies]) =>
   new PackagesFileDescriptor(dependencies);