Fix flakiness in physical_resource_provider_test

pkg/analyzer/test/file_system/physical_resource_provider_test.dart

 // Copyright (c) 2014, 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 test.physical_file_system;
 
 import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 50 matching lines @@
             subscription.cancel();
           });
         });
       }
 
       test('create file', () => watchingFolder(tempPath, (changesReceived) {
         expect(changesReceived, hasLength(0));
         var path = join(tempPath, 'foo');
         new io.File(path).writeAsStringSync('contents');
         return delayed(() {
-          expect(changesReceived, hasLength(1));
+          // There should be an "add" event indicating that the file was added.
+          // Depending on how long it took to write the contents, it may be
+          // followed by "modify" events.
+          expect(changesReceived, isNotEmpty);
           expect(changesReceived[0].type, equals(ChangeType.ADD));
           expect(changesReceived[0].path, equals(path));
+          for (int i = 1; i < changesReceived.length; i++) {
+            expect(changesReceived[i].type, equals(ChangeType.MODIFY));
+            expect(changesReceived[i].path, equals(path));
+          }
         });
       }));
 
       test('modify file', () {
         var path = join(tempPath, 'foo');
         var file = new io.File(path);
         file.writeAsStringSync('contents 1');
         return watchingFolder(tempPath, (changesReceived) {
           expect(changesReceived, hasLength(0));
           file.writeAsStringSync('contents 2');
@@ skipping 241 matching lines @@
         expect(
             folder.canonicalizePath(join('.', 'baz')),
             equals(join(path, 'baz')));
         expect(
             folder.canonicalizePath(join(path2, '.', 'baz')),
             equals(join(path2, 'baz')));
       });
     });
   });
 }