fix uri contributor for Windows

pkg/analysis_server/lib/src/services/completion/dart/uri_contributor.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 services.completion.contributor.dart.importuri;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
@@ skipping 103 matching lines @@
 
     String dirPath = resContext.normalize(parentUri);
     if (resContext.isRelative(dirPath)) {
       String sourceDirPath = resContext.dirname(source.fullName);
       if (resContext.isAbsolute(sourceDirPath)) {
         dirPath = resContext.join(sourceDirPath, dirPath);
       } else {
         return;
       }
     }
+    if (dirPath.endsWith('\\.')) {
+      dirPath = dirPath.substring(0, dirPath.length - 1);
+    }
 
     Resource dir = resProvider.getResource(dirPath);
     if (dir is Folder) {
       for (Resource child in dir.getChildren()) {
         String completion;
         if (child is Folder) {
           completion = '$uriPrefix${child.shortName}/';
         } else {
           completion = '$uriPrefix${child.shortName}';
         }
@@ skipping 43 matching lines @@
   }
 
   String _extractPartialUri(SimpleStringLiteral node) {
     if (request.offset < node.contentsOffset) {
       return null;
     }
     return node.literal.lexeme.substring(
         node.contentsOffset - node.offset, request.offset - node.offset);
   }
 }