Fix more tests on windows bots

pkg/analyzer/test/src/task/dart_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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 3358 matching lines @@
     Iterable<String> shortNames = sources.map((s) => s.shortName);
     if (shortNames.length == 2) {
       expect(shortNames, unorderedEquals(['core.dart', expectedShortName]));
     } else {
       expect(shortNames, unorderedEquals([expectedShortName]));
     }
   }
 
   void _performParseTask(String content) {
     if (content == null) {
-      source = resourceProvider.getFile('/test.dart').createSource();
+      source = resourceProvider
+          .getFile(resourceProvider.convertPath('/test.dart'))
+          .createSource();
     } else {
       source = newSource('/test.dart', content);
     }
     computeResult(source, PARSED_UNIT, matcher: isParseDartTask);
   }
 
   static void _assertHasCore(dynamic sourceList, int lenght) {
     List<Source> sources = sourceList as List<Source>;
     expect(sources, hasLength(lenght));
     expect(sources, contains(predicate((Source s) {
@@ skipping 2263 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result] as List<AnalysisError>;
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }