Make pub strong-mode clean.

lib/src/source/hosted.dart

 // Copyright (c) 2012, 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:async';
 import 'dart:io' as io;
 import "dart:convert";
 
 import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as p;
@@ skipping 194 matching lines @@
     var parsed = source._parseDescription(id.description);
     var dir = _urlToDirectory(parsed.last);
     return p.join(systemCacheRoot, dir, "${parsed.first}-${id.version}");
   }
 
   /// Re-downloads all packages that have been previously downloaded into the
   /// system cache from any server.
   Future<Pair<List<PackageId>, List<PackageId>>> repairCachedPackages() async {
     if (!dirExists(systemCacheRoot)) return new Pair([], []);
 
-    var successes = [];
-    var failures = [];
+    var successes = <PackageId>[];
+    var failures = <PackageId>[];
 
     for (var serverDir in listDir(systemCacheRoot)) {
       var url = _directoryToUrl(p.basename(serverDir));
       var packages = _getCachedPackagesInDirectory(p.basename(serverDir));
       packages.sort(Package.orderByNameAndVersion);
 
       for (var package in packages) {
         var id = source.idFor(package.name, package.version, url: url);
 
         try {
@@ skipping 192 matching lines @@
     // Since HostedSource is cached, this will only be called for uncached
     // packages.
     throw new UnsupportedError("Cannot download packages when offline.");
   }
 
   Future<Pubspec> describeUncached(PackageId id) {
     throw new PackageNotFoundException(
         "${id.name} ${id.version} is not available in your system cache.");
   }
 }