Fixes for the 'pub' bot and 'analysis_server' on Windows.

pkg/analyzer/lib/file_system/memory_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 memory_file_system;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
@@ skipping 168 matching lines @@
       throw new MemoryResourceException(path, "File '$path' does not exist");
     }
     return content;
   }
 
   int get _timestamp => _provider._pathToTimestamp[path];
 
   @override
   Source createSource([Uri uri]) {
     if (uri == null) {
-      uri = toUri(path);
+      uri = posix.toUri(path);
     }
     return new _MemoryFileSource(this, uri);
   }
 }
 
 
 /**
  * An in-memory implementation of [Source].
  */
 class _MemoryFileSource implements Source {
@@ skipping 151 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }