Removed fixed dependencies

packages/package_config/lib/src/packages_impl.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.
 
 /// Implementations of [Packages] that may be used in either server or browser
 /// based applications. For implementations that can only run in the browser,
 /// see [package_config.packages_io_impl].
 library package_config.packages_impl;
 
 import "dart:collection" show UnmodifiableMapView;
+
 import "../packages.dart";
 import "util.dart" show checkValidPackageUri;
 
 /// A [Packages] null-object.
 class NoPackages implements Packages {
   const NoPackages();
 
   Uri resolve(Uri packageUri, {Uri notFound(Uri packageUri)}) {
     String packageName = checkValidPackageUri(packageUri);
     if (notFound != null) return notFound(packageUri);
@@ skipping 64 matching lines @@
   }
 
   Iterable<String> get packages {
     throw _failListingPackages();
   }
 
   Map<String, Uri> asMap() {
     throw _failListingPackages();
   }
 }