Fix multiple onRequest callbacks during redirect.

sdk/lib/io/http_impl.dart

 // Copyright (c) 2012, 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.
 
 class _HttpHeaders implements HttpHeaders {
   _HttpHeaders() : _headers = new Map<String, List<String>>();
 
   List<String> operator[](String name) {
     name = name.toLowerCase();
     return _headers[name];
@@ skipping 2311 matching lines @@
   }
 
   HttpClientConnection _prepareHttpClientConnection(
       String method,
       Uri url,
       [_HttpClientConnection connection]) {
 
     void _establishConnection(String host,
                               int port,
                               _ProxyConfiguration proxyConfiguration,
-                              int proxyIndex) {
+                              int proxyIndex,
+                              bool reusedConnection) {
 
       void _connectionOpened(_SocketConnection socketConn,
                              _HttpClientConnection connection,
                              bool usingProxy) {
         connection._usingProxy = usingProxy;
         connection._connectionEstablished(socketConn);
         HttpClientRequest request = connection.open(method, url);
         request.headers.host = host;
         request.headers.port = port;
         if (url.userInfo != null && !url.userInfo.isEmpty) {
           // If the URL contains user information use that for basic
           // authorization
           _UTF8Encoder encoder = new _UTF8Encoder();
           String auth =
               CryptoUtils.bytesToBase64(encoder.encodeString(url.userInfo));
           request.headers.set(HttpHeaders.AUTHORIZATION, "Basic $auth");
         } else {
           // Look for credentials.
           _Credentials cr = _findCredentials(url);
           if (cr != null) {
             cr.authorize(request);
           }
         }
-        if (connection._onRequest != null) {
+        // A reused connection is indicating either redirect or retry
+        // where the onRequest callback should not be issued again.
+        if (connection._onRequest != null && !reusedConnection) {
           connection._onRequest(request);
         } else {
           request.outputStream.close();
         }
       }
 
       assert(proxyIndex < proxyConfiguration.proxies.length);
 
       // Determine the actual host to connect to.
       String connectHost;
@@ skipping 48 matching lines @@
         if (socketConnections.isEmpty) _openSockets.remove(key);
         if (_openSockets.isEmpty) _cancelEvictionTimer();
       }
     }
 
     // Find the TCP host and port.
     String host = url.domain;
     int port = url.port == 0 ? HttpClient.DEFAULT_HTTP_PORT : url.port;
 
     // Create a new connection object if we are not re-using an existing one.
+    var reusedConnection = false;
     if (connection == null) {
       connection = new _HttpClientConnection(this);
+    } else {
+      reusedConnection = true;
     }
     connection.onDetach = () => _activeSockets.remove(connection._socketConn);
 
     // Check to see if a proxy server should be used for this connection.
     _ProxyConfiguration proxyConfiguration = const _ProxyConfiguration.direct();
     if (_findProxy != null) {
       // TODO(sgjesse): Keep a map of these as normally only a few
       // configuration strings will be used.
       proxyConfiguration = new _ProxyConfiguration(_findProxy(url));
     }
 
     // Establish the connection starting with the first proxy configured.
-    _establishConnection(host, port, proxyConfiguration, 0);
+    _establishConnection(host, port, proxyConfiguration, 0, reusedConnection);
 
     return connection;
   }
 
   void _returnSocketConnection(_SocketConnection socketConn) {
     // Mark socket as returned to unregister from the old connection.
     socketConn._markReturned();
 
     // If the HTTP client is beeing shutdown don't return the connection.
     if (_shutdown) {
@@ skipping 198 matching lines @@
 
 
 class _RedirectInfo implements RedirectInfo {
   const _RedirectInfo(int this.statusCode,
                       String this.method,
                       Uri this.location);
   final int statusCode;
   final String method;
   final Uri location;
 }