pkg/test: Resolve a number of analyzer 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 12 matching lines @@
 import 'plugin/hack_register_platform.dart';
 import 'plugin/platform.dart';
 import 'runner_suite.dart';
 import 'vm/platform.dart';
 
 /// A class for finding test files and loading them into a runnable form.
 class Loader {
   /// The test runner configuration.
   final Configuration _config;
 
-  /// The root directory that will be served for browser tests.
-  final String _root;
-
   /// All suites that have been created by the loader.
   final _suites = new Set<RunnerSuite>();
 
   /// Memoizers for platform plugins, indexed by the platforms they support.
   final _platformPlugins = <TestPlatform, AsyncMemoizer<PlatformPlugin>>{};
 
   /// The functions to use to load [_platformPlugins].
   ///
   /// These are passed to the plugins' async memoizers when a plugin is needed.
   final _platformCallbacks = <TestPlatform, AsyncFunction>{};
 
   /// Creates a new loader that loads tests on platforms defined in [_config].
   ///
   /// [root] is the root directory that will be served for browser tests. It
   /// defaults to the working directory.
-  Loader(this._config, {String root})
-      : _root = root == null ? p.current : root {
+  Loader(this._config, {String root}) {
     registerPlatformPlugin([TestPlatform.vm], () => new VMPlatform(_config));
     registerPlatformPlugin([
       TestPlatform.dartium,
       TestPlatform.contentShell,
       TestPlatform.chrome,
       TestPlatform.phantomJS,
       TestPlatform.firefox,
       TestPlatform.safari,
       TestPlatform.internetExplorer
     ], () => BrowserPlatform.start(_config, root: root));
@@ skipping 118 matching lines @@
       })),
       Future.wait(_suites.map((suite) => suite.close()))
     ]);
 
     _platformPlugins.clear();
     _platformCallbacks.clear();
     _suites.clear();
   });
   final _closeMemo = new AsyncMemoizer();
 }