MemoryResourceProvider.getFolder() should not create the folder.

pkg/analysis_server/test/source/caching_put_package_map_provider_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.
 
 library test.source.caching_pub_package_map_provider;
 
 import 'dart:convert';
 import 'dart:core';
 import 'dart:io' as io;
 
@@ skipping 50 matching lines @@
         resProvider.modifyFile(cacheFile.path, content);
       }
       Resource res = resProvider.getResource(cacheFile.path);
       if (res is File) {
         return res.createSource().modificationStamp;
       }
       throw 'expected file, but found $res';
     }
 
     CachingPubPackageMapProvider newPkgProvider() {
+      Folder sdkFolder = resProvider
+          .newFolder(resProvider.convertPath('/Users/user/dart-sdk'));
       return new CachingPubPackageMapProvider(
           resProvider,
-          new FolderBasedDartSdk(
-              resProvider, FolderBasedDartSdk.defaultSdkDirectory(resProvider)),
+          new FolderBasedDartSdk(resProvider, sdkFolder),
           mockRunner.runPubList,
           mockWriteFile);
     }
 
     setUp(() {
       resProvider = new MemoryResourceProvider();
       resProvider.newFolder('/tmp/proj/packages/foo');
       mockRunner = new _MockPubListRunner();
       writeFileException = false;
     });
@@ skipping 306 matching lines @@
       provider.newFolder(path);
     }
     int fileCount = _filePaths.length;
     for (int fileIndex = 0; fileIndex < fileCount; ++fileIndex) {
       String path = _filePaths[fileIndex];
       TimestampedData content = _fileContents[fileIndex];
       provider.newFile(path, content.data, content.modificationTime);
     }
   }
 }