fix MemoryResourceProvider context 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/source/package_map_resolver.dart';
 import 'package:analyzer/src/command_line/arguments.dart';
@@ skipping 704 matching lines @@
     _expectEqualOptions(options, expected);
   }
 
   void test_getAnalysisOptions_default_flutter() {
     _defineMockLintRules();
     AnalysisOptionsImpl defaultOptions = new AnalysisOptionsImpl();
     builderOptions.defaultOptions = defaultOptions;
     AnalysisOptionsImpl expected = new AnalysisOptionsImpl();
     expected.lint = true;
     expected.lintRules = <Linter>[_mockLintRule];
+    String packagesFilePath =
+        resourceProvider.convertPath('/some/directory/path/.packages');
+    createFile(packagesFilePath, 'flutter:/pkg/flutter/lib/');
+    String optionsFilePath = resourceProvider
+        .convertPath('/pkg/flutter/lib/analysis_options_user.yaml');
     createFile(
-        resourceProvider.convertPath('/some/directory/path/.packages'),
-        '''
-flutter:/pkg/flutter/lib/
-''');
-    createFile(
-        resourceProvider
-            .convertPath('/pkg/flutter/lib/analysis_options_user.yaml'),
+        optionsFilePath,
         '''
 linter:
   rules:
     - mock_lint_rule
 ''');
-    AnalysisOptions options = builder.getAnalysisOptions(
-        resourceProvider.convertPath('/some/directory/path'));
-    // TODO(danrubel) fix on Windows
-    if (resourceProvider.absolutePathContext.separator != r'\') {
-      _expectEqualOptions(options, expected);
-    }
+    String projPath = resourceProvider.convertPath('/some/directory/path');
+    AnalysisOptions options = builder.getAnalysisOptions(projPath);
+    _expectEqualOptions(options, expected);
   }
 
   void test_getAnalysisOptions_default_noOverrides() {
     AnalysisOptionsImpl defaultOptions = new AnalysisOptionsImpl();
     defaultOptions.enableLazyAssignmentOperators = true;
     builderOptions.defaultOptions = defaultOptions;
     AnalysisOptionsImpl expected = new AnalysisOptionsImpl();
     expected.enableLazyAssignmentOperators = true;
     String path = resourceProvider.convertPath('/some/directory/path');
     String filePath =
@@ skipping 259 matching lines @@
 class _MockLintRule implements LintRule {
   final String _name;
 
   _MockLintRule(this._name);
 
   @override
   String get name => _name;
 
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }