Fixes for ContextBuilder and tests to make them pass on Windows.

pkg/analyzer/lib/src/context/builder.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.src.context.context_builder;
 
 import 'dart:collection';
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/plugin/resolver_provider.dart';
 import 'package:analyzer/source/analysis_options_provider.dart';
 import 'package:analyzer/source/embedder.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/source/sdk_ext.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/task/options.dart';
 import 'package:package_config/discovery.dart';
 import 'package:package_config/packages.dart';
 import 'package:package_config/packages_file.dart';
 import 'package:package_config/src/packages_impl.dart';
-import 'package:path/path.dart' as path;
 import 'package:yaml/yaml.dart';
 
 /**
  * A utility class used to build an analysis context for a given directory.
  *
  * The construction of analysis contexts is as follows:
  *
  * 1. Determine how package: URI's are to be resolved. This follows the lookup
  *    algorithm defined by the [package specification][1].
  *
@@ skipping 100 matching lines @@
 //      optionsProcessors.forEach((OptionsProcessor p) => p.onError(e));
 //    }
 //  }
 
   Map<String, List<Folder>> convertPackagesToMap(Packages packages) {
     if (packages == null || packages == Packages.noPackages) {
       return null;
     }
     Map<String, List<Folder>> folderMap = new HashMap<String, List<Folder>>();
     packages.asMap().forEach((String packagePath, Uri uri) {
-      folderMap[packagePath] = [resourceProvider.getFolder(path.fromUri(uri))];
+      String path = resourceProvider.pathContext.fromUri(uri);
+      folderMap[packagePath] = [resourceProvider.getFolder(path)];
     });
     return folderMap;
   }
 
   Packages createPackageMap(String rootDirectoryPath) {
     if (defaultPackageFilePath != null) {
       // TODO(brianwilkerson) Figure out why we're going through Uri rather than
       // just creating the file from the path.
       Uri fileUri = new Uri.file(defaultPackageFilePath);
       io.File configFile = new io.File.fromUri(fileUri).absolute;
@@ skipping 125 matching lines @@
       }
       file = folder
           .getChildAssumingFile(AnalysisEngine.ANALYSIS_OPTIONS_YAML_FILE);
       if (file.exists) {
         return file;
       }
     }
     return null;
   }
 }