Get more tests passing on windows

pkg/analyzer/test/src/dart/sdk/sdk_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.generated.sdk_test;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/context/builder.dart' show EmbedderYamlLocator;
 import 'package:analyzer/src/dart/sdk/sdk.dart';
@@ skipping 256 matching lines @@
   }
 
   void test_useSummary_beforeContextCreation() {
     FolderBasedDartSdk sdk = _createDartSdk();
     sdk.useSummary = true;
     sdk.context;
   }
 
   FolderBasedDartSdk _createDartSdk() {
     resourceProvider = new MemoryResourceProvider();
-    Folder sdkDirectory = resourceProvider.getFolder('/sdk');
+    Folder sdkDirectory =
+        resourceProvider.getFolder(resourceProvider.convertPath('/sdk'));
     _createFile(sdkDirectory,
         ['lib', '_internal', 'sdk_library_metadata', 'lib', 'libraries.dart'],
         content: _librariesFileContent());
     _createFile(sdkDirectory, ['bin', 'dart']);
     _createFile(sdkDirectory, ['bin', 'dart2js']);
     _createFile(sdkDirectory, ['bin', 'pub']);
     _createFile(sdkDirectory, ['lib', 'async', 'async.dart']);
     _createFile(sdkDirectory, ['lib', 'core', 'core.dart']);
     _createFile(sdkDirectory, ['lib', 'core', 'num.dart']);
     _createFile(sdkDirectory,
@@ skipping 170 matching lines @@
     expect(second, isNotNull);
     expect(second.category, "Server");
     expect(second.path, "second/second.dart");
     expect(second.shortName, "dart:second");
     expect(second.isDart2JsLibrary, false);
     expect(second.isDocumented, false);
     expect(second.isImplementation, true);
     expect(second.isVmLibrary, false);
   }
 }