Process outstanding events before making a new HTTP client request

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 _OUTGOING_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 1865 matching lines @@
     Future<_ConnectionInfo> connect(error) {
       if (!proxies.moveNext()) return new Future.error(error);
       _Proxy proxy = proxies.current;
       String host = proxy.isDirect ? uriHost: proxy.host;
       int port = proxy.isDirect ? uriPort: proxy.port;
       return _getConnectionTarget(host, port, isSecure)
           .connect(uriHost, uriPort, proxy, this)
           // On error, continue with next proxy.
           .catchError(connect);
     }
-    return connect(new HttpException("No proxies given"));
+    // Make sure we go through the event loop before taking a
+    // connection from the pool. For long-running synchronous code the
+    // server might have closed the connection, so this lowers the
+    // probability of getting a connection that was already closed.
+    return new Future(() => connect(new HttpException("No proxies given")));
   }
 
   _SiteCredentials _findCredentials(Uri url, [_AuthenticationScheme scheme]) {
     // Look for credentials.
     _SiteCredentials cr =
         _credentials.fold(null, (prev, value) {
           if (value.applies(url, scheme)) {
             if (prev == null) return value;
             return value.uri.path.length > prev.uri.path.length ? value : prev;
           } else {
@@ skipping 915 matching lines @@
   const _RedirectInfo(this.statusCode, this.method, this.location);
 }
 
 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)';
 }