MemoryResourceProvider.getFolder() should not create the folder.

pkg/analyzer/test/file_system/memory_file_system_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 analyzer.test.file_system.memory_file_system_test;
 
 import 'dart:async';
 import 'dart:core';
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 605 matching lines @@
     expect(file.exists, isFalse);
   }
 
   test_getModificationTimes() async {
     File file = provider.newFile(provider.convertPath('/test.dart'), '');
     Source source = file.createSource();
     List<int> times = await provider.getModificationTimes([source]);
     expect(times, [source.modificationStamp]);
   }
 
+  test_getFolder_existing() async {
+    String path = provider.convertPath('/foo/bar');
+    provider.newFolder(path);
+    Folder folder = provider.getFolder(path);
+    expect(folder, isNotNull);
+    expect(folder.path, path);
+    expect(folder.exists, isTrue);
+  }
+
+  test_getFolder_notExisting() async {
+    String path = provider.convertPath('/foo/bar');
+    Folder folder = provider.getFolder(path);
+    expect(folder, isNotNull);
+    expect(folder.path, path);
+    expect(folder.exists, isFalse);
+  }
+
   void test_getStateLocation_uniqueness() {
     String idOne = 'one';
     Folder folderOne = provider.getStateLocation(idOne);
     expect(folderOne, isNotNull);
     String idTwo = 'two';
     Folder folderTwo = provider.getStateLocation(idTwo);
     expect(folderTwo, isNotNull);
     expect(folderTwo, isNot(equals(folderOne)));
     expect(provider.getStateLocation(idOne), equals(folderOne));
   }
@@ skipping 133 matching lines @@
     return new Future.delayed(Duration.ZERO, computation);
   }
 
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     Folder folder = provider.getResource(path);
     var changesReceived = <WatchEvent>[];
     folder.changes.listen(changesReceived.add);
     return test(changesReceived);
   }
 }