Fix more tests on windows bots

pkg/analyzer/test/src/task/strong/strong_test_helper.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.
 
 // TODO(jmesserly): this file needs to be refactored, it's a port from
 // package:dev_compiler's tests
 library analyzer.test.src.task.strong.strong_test_helper;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 44 matching lines @@
 /// See [addFile] for more information about how to encode expectations in
 /// the file text.
 ///
 /// Returns the main resolved library. This can be used for further checks.
 CompilationUnit check(
     {bool implicitCasts: true,
     bool implicitDynamic: true,
     List<String> nonnullableTypes: AnalysisOptionsImpl.NONNULLABLE_TYPES}) {
   _checkCalled = true;
 
-  expect(files.getFile(files.convertPath('/main.dart')).exists, true,
-      reason: '`/main.dart` is missing');
+  File mainFile = files.getFile(files.convertPath('/main.dart'));
+  expect(mainFile.exists, true, reason: '`/main.dart` is missing');
 
   var uriResolver = new _TestUriResolver(files);
   // Enable task model strong mode
   var context = AnalysisEngine.instance.createAnalysisContext();
   AnalysisOptionsImpl options = context.analysisOptions as AnalysisOptionsImpl;
   options.strongMode = true;
   options.strongModeHints = true;
   options.implicitCasts = implicitCasts;
   options.implicitDynamic = implicitDynamic;
   options.nonnullableTypes = nonnullableTypes;
-  var mockSdk = new MockSdk();
+  var mockSdk = new MockSdk(resourceProvider: files);
   (mockSdk.context.analysisOptions as AnalysisOptionsImpl).strongMode = true;
   context.sourceFactory =
       new SourceFactory([new DartUriResolver(mockSdk), uriResolver]);
 
   // Run the checker on /main.dart.
-  Source mainSource = uriResolver.resolveAbsolute(new Uri.file('/main.dart'));
+  Source mainSource = uriResolver.resolveAbsolute(mainFile.toUri());
   var initialLibrary = context.resolveCompilationUnit2(mainSource, mainSource);
 
   var collector = new _ErrorCollector(context);
 
   // Extract expectations from the comments in the test files, and
   // check that all errors we emit are included in the expected map.
   var allLibraries = _reachableLibraries(initialLibrary.element.library);
   for (var lib in allLibraries) {
     for (var unit in lib.units) {
       var errors = <AnalysisError>[];
@@ skipping 299 matching lines @@
 
 class _TestUriResolver extends ResourceUriResolver {
   final MemoryResourceProvider provider;
   _TestUriResolver(provider)
       : provider = provider,
         super(provider);
 
   @override
   Source resolveAbsolute(Uri uri, [Uri actualUri]) {
     if (uri.scheme == 'package') {
-      return (provider.getResource('/packages/' + uri.path) as File)
+      return (provider.getResource(
+              provider.convertPath('/packages/' + uri.path)) as File)
           .createSource(uri);
     }
     return super.resolveAbsolute(uri, actualUri);
   }
 }