Use AbsolutePathContext in Folder.contains().

pkg/analyzer/lib/file_system/physical_file_system.dart

 // Copyright (c) 2014, 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 physical_file_system;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/source_io.dart';
+import 'package:analyzer/src/util/absolute_path.dart';
 import 'package:path/path.dart';
 import 'package:watcher/watcher.dart';
 
 import 'file_system.dart';
 
 /**
  * A `dart:io` based implementation of [ResourceProvider].
  */
 class PhysicalResourceProvider implements ResourceProvider {
   static final NORMALIZE_EOL_ALWAYS = (String string) =>
       string.replaceAll(new RegExp('\r\n?'), '\n');
 
   static final PhysicalResourceProvider INSTANCE =
       new PhysicalResourceProvider(null);
 
   /**
    * The name of the directory containing plugin specific subfolders used to
    * store data across sessions.
    */
   static final String SERVER_DIR = ".dartServer";
 
+  final AbsolutePathContext absolutePathContext =
+      new AbsolutePathContext(io.Platform.pathSeparator);
+
   PhysicalResourceProvider(String fileReadMode(String s)) {
     if (fileReadMode != null) {
       FileBasedSource.fileReadMode = fileReadMode;
     }
   }
 
   @override
   Context get pathContext => io.Platform.isWindows ? windows : posix;
 
   @override
@@ skipping 78 matching lines @@
  * A `dart:io` based implementation of [Folder].
  */
 class _PhysicalFolder extends _PhysicalResource implements Folder {
   _PhysicalFolder(io.Directory directory) : super(directory);
 
   @override
   Stream<WatchEvent> get changes => new DirectoryWatcher(_entry.path).events;
 
   @override
   String canonicalizePath(String relPath) {
-    return normalize(join(_entry.absolute.path, relPath));
+    return normalize(join(path, relPath));
   }
 
   @override
   bool contains(String path) {
-    return isWithin(this.path, path);
+    return absolutePathContext.isWithin(this.path, path);
   }
 
   @override
   Resource getChild(String relPath) {
     String canonicalPath = canonicalizePath(relPath);
     return PhysicalResourceProvider.INSTANCE.getResource(canonicalPath);
   }
 
   @override
   _PhysicalFolder getChildAssumingFolder(String relPath) {
@@ skipping 33 matching lines @@
 }
 
 /**
  * A `dart:io` based implementation of [Resource].
  */
 abstract class _PhysicalResource implements Resource {
   final io.FileSystemEntity _entry;
 
   _PhysicalResource(this._entry);
 
+  AbsolutePathContext get absolutePathContext =>
+      PhysicalResourceProvider.INSTANCE.absolutePathContext;
+
   @override
   bool get exists => _entry.existsSync();
 
   @override
   get hashCode => path.hashCode;
 
   @override
   Folder get parent {
-    String parentPath = dirname(path);
+    String parentPath = absolutePathContext.dirname(path);
     if (parentPath == path) {
       return null;
     }
     return new _PhysicalFolder(new io.Directory(parentPath));
   }
 
   @override
   String get path => _entry.absolute.path;
 
   @override
-  String get shortName => basename(path);
+  String get shortName => absolutePathContext.basename(path);
 
   @override
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }