Fix context/builder_test.dart on Windows.

pkg/analyzer/test/src/context/builder_test.dart

 // Copyright (c) 2016, 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.src.context.context_builder_test;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/plugin/options.dart';
 import 'package:analyzer/src/context/builder.dart';
@@ skipping 78 matching lines @@
 
   void createFile(String path, String content) {
     resourceProvider.newFile(path, content);
   }
 
   @override
   void setUp() {
     resourceProvider = new MemoryResourceProvider();
     pathContext = resourceProvider.pathContext;
     new MockSdk(resourceProvider: resourceProvider);
-    sdkManager = new DartSdkManager('/sdk', false, (_) {
+    sdkManager =
+        new DartSdkManager(resourceProvider.convertPath('/sdk'), false, (_) {
       fail('Should not be used to create an SDK');
     });
     contentCache = new ContentCache();
     builder = new ContextBuilder(resourceProvider, sdkManager, contentCache);
   }
 
   @failingTest
   void test_buildContext() {
     fail('Incomplete test');
   }
@@ skipping 628 matching lines @@
       fail('Unexpected invocation of optionsProcessed');
     }
     expect(options, hasLength(expectedOptions.length));
     for (String key in expectedOptions.keys) {
       expect(options.containsKey(key), isTrue, reason: 'missing key $key');
       expect(options[key], expectedOptions[key],
           reason: 'values for key $key do not match');
     }
   }
 }