pkg/test: cleanup imports

test/backend/metadata_test.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 'package:test/src/backend/metadata.dart';
 import 'package:test/src/backend/test_platform.dart';
+import 'package:test/src/frontend/skip.dart';
 import 'package:test/src/frontend/timeout.dart';
-import 'package:test/src/frontend/skip.dart';
 import 'package:test/test.dart';
 
 void main() {
   group("tags", () {
     test("parses an Iterable", () {
       expect(new Metadata.parse(tags: ["a", "b"]).tags,
           unorderedEquals(["a", "b"]));
     });
 
     test("parses a String", () {
@@ skipping 129 matching lines @@
       }, throwsArgumentError);
     });
 
     test("refuses multiple Skips", () {
       expect(() {
         new Metadata.parse(onPlatform: {"chrome": [new Skip(), new Skip()]});
       }, throwsArgumentError);
     });
   });
 }