Update the Linux watcher to accommodate changes in [Directory.watch].

pkg/watcher/test/directory_watcher/linux_test.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.
 
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:watcher/src/directory_watcher/linux.dart';
 import 'package:watcher/watcher.dart';
 
 import 'shared.dart';
 import '../utils.dart';
 
 main() {
   initConfig();
 
   watcherFactory = (dir) => new LinuxDirectoryWatcher(dir);
 
-  setUp(() {
-    // Increase the timeout because closing a [Directory.watch] stream blocks
-    // the main isolate for a very long time on Goobuntu, as of kernel
-    // 3.2.5-gg1336 (see issue 14606).
-    currentSchedule.timeout *= 3;
-
-    createSandbox();
-  });
+  setUp(createSandbox);
 
   sharedTests();
 
   test('DirectoryWatcher creates a LinuxDirectoryWatcher on Linux', () {
     expect(new DirectoryWatcher('.'),
         new isInstanceOf<LinuxDirectoryWatcher>());
   });
 
   test('notifies even if the file contents are unchanged', () {
     writeFile("a.txt", contents: "same");
@@ skipping 18 matching lines @@
       withPermutations((i, j, k) =>
           expectRemoveEvent("dir/sub/sub-$i/sub-$j/file-$k.txt"));
     });
 
     inAnyOrder(() {
       withPermutations((i, j, k) =>
           expectAddEvent("dir/sub/sub-$i/sub-$j/file-$k.txt"));
     });
   });
 }