Fix all strong-mode errors and warnings.

lib/src/runner/loader.dart

 // Copyright (c) 2015, 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';
 
 import 'package:analyzer/analyzer.dart' hide Configuration;
 import 'package:async/async.dart';
 import 'package:path/path.dart' as p;
@@ skipping 58 matching lines @@
   /// Registers a [PlatformPlugin] for [platforms].
   ///
   /// When the runner first requests that a suite be loaded for one of the given
   /// platforms, this will call [getPlugin] to load the platform plugin. It may
   /// return either a [PlatformPlugin] or a [Future<PlatformPlugin>]. That
   /// plugin is then preserved and used to load all suites for all matching
   /// platforms.
   ///
   /// This overwrites previous plugins for those platforms.
   void registerPlatformPlugin(Iterable<TestPlatform> platforms, getPlugin()) {
-    var memoizer = new AsyncMemoizer();
+    var memoizer = new AsyncMemoizer<PlatformPlugin>();
     for (var platform in platforms) {
       _platformPlugins[platform] = memoizer;
       _platformCallbacks[platform] = getPlugin;
     }
   }
 
   /// Loads all test suites in [dir].
   ///
   /// This will load tests from files that match the configuration's filename
   /// glob. Any tests that fail to load will be emitted as [LoadException]s.
   ///
   /// This emits [LoadSuite]s that must then be run to emit the actual
   /// [RunnerSuite]s defined in the file.
   Stream<LoadSuite> loadDir(String dir) {
-    return mergeStreams(new Directory(dir).listSync(recursive: true)
+    return StreamGroup.merge(new Directory(dir).listSync(recursive: true)
         .map((entry) {
       if (entry is! File) return new Stream.fromIterable([]);
 
       if (!_config.filename.matches(p.basename(entry.path))) {
         return new Stream.fromIterable([]);
       }
 
       if (p.split(entry.path).contains('packages')) {
          return new Stream.fromIterable([]);
       }
@@ skipping 76 matching lines @@
       })),
       Future.wait(_suites.map((suite) => suite.close()))
     ]);
 
     _platformPlugins.clear();
     _platformCallbacks.clear();
     _suites.clear();
   });
   final _closeMemo = new AsyncMemoizer();
 }