Use 'Directory.watch' on Windows in pkg/watcher, instead of pooling.

pkg/watcher/test/utils.dart

 // Copyright (c) 2012, 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.
 
 library watcher.test.utils;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 53 matching lines @@
     // Make sure we got a path in the sandbox.
     assert(p.isRelative(path) && !path.startsWith(".."));
 
     var mtime = _mockFileModificationTimes[path];
     return new DateTime.fromMillisecondsSinceEpoch(mtime == null ? 0 : mtime);
   });
 
   // Delete the sandbox when done.
   currentSchedule.onComplete.schedule(() {
     if (_sandboxDir != null) {
+      // TODO(rnystrom): Issue 19155. The watcher should already be closed when
+      // we clean up the sandbox.
+      if (_watcherEvents != null) {
+        _watcherEvents.close();
+      }
       new Directory(_sandboxDir).deleteSync(recursive: true);
       _sandboxDir = null;
     }
 
     _mockFileModificationTimes = null;
     mockGetModificationTime(null);
   }, "delete sandbox");
 }
 
 /// Creates a new [DirectoryWatcher] that watches a temporary directory.
@@ skipping 301 matching lines @@
   var results = new Set();
   for (var i = 0; i < limit; i++) {
     for (var j = 0; j < limit; j++) {
       for (var k = 0; k < limit; k++) {
         results.add(callback(i, j, k));
       }
     }
   }
   return results;
 }