Fix analyzer hints and warnings in test/.

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.
 library descriptor;
 
-import "dart:io" show File;
-
 import 'package:oauth2/oauth2.dart' as oauth2;
-import 'package:path/path.dart' as p;
 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';
-import 'package:package_config/packages_file.dart' as packages_file;
-import 'package:stack_trace/stack_trace.dart';
 
 import 'descriptor/git.dart';
 import 'descriptor/tar.dart';
 import 'descriptor/packages.dart';
 import 'test_pub.dart';
 
 export 'package:scheduled_test/descriptor.dart';
 export 'descriptor/git.dart';
 export 'descriptor/tar.dart';
 export 'descriptor/packages.dart';
@@ skipping 168 matching lines @@
 /// 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]) =>
   new PackagesFileDescriptor(dependencies);