Fix bug in handling IPv6 proxy hosts

sdk/lib/io/http_impl.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 const int _HEADERS_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 2183 matching lines @@
             password = userinfo.substring(colon + 1).trim();
           }
           // Look for proxy host and port.
           int colon = proxy.lastIndexOf(":");
           if (colon == -1 || colon == 0 || colon == proxy.length - 1) {
             throw new HttpException(
                 "Invalid proxy configuration $configuration");
           }
           String host = proxy.substring(0, colon).trim();
           if (host.startsWith("[") && host.endsWith("]")) {
-            host = host.substring(1, host.length - 2);
+            host = host.substring(1, host.length - 1);
           }
           String portString = proxy.substring(colon + 1).trim();
           int port;
           try {
             port = int.parse(portString);
           } on FormatException catch (e) {
             throw new HttpException(
                 "Invalid proxy configuration $configuration, "
                 "invalid port '$portString'");
           }
@@ skipping 355 matching lines @@
 
 String _getHttpVersion() {
   var version = Platform.version;
   // Only include major and minor version numbers.
   int index = version.indexOf('.', version.indexOf('.') + 1);
   version = version.substring(0, index);
   return 'Dart/$version (dart:io)';
 }