Add support for HTTP proxy in the HTTP client

runtime/bin/http.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.
 
 /**
  * HTTP status codes.
  */
 abstract class HttpStatus {
   static const int CONTINUE = 100;
   static const int SWITCHING_PROTOCOLS = 101;
@@ skipping 691 matching lines @@
    * Opens a HTTP connection using the POST method. See [open] for details.
    */
   HttpClientConnection post(String host, int port, String path);
 
   /**
    * Opens a HTTP connection using the POST method. See [openUrl] for details.
    */
   HttpClientConnection postUrl(Uri url);
 
   /**
+   * Sets the function used to resolve the proxy server to be used for
+   * opening a HTTP connection to the specified [url]. If this
+   * function is not set, direct connections will always be used.
+   *
+   * The string returned by [f] must be in the format used by browser
+   * PAC (proxy auto-config) scripts. That is either
+   *
+   *   "DIRECT"
+   *
+   * for using a direct connection or
+   *
+   *   "PROXY host:port"
+   *
+   * for using the proxy server [:host:] on port [:port:].
+   *
+   * A configuration can contain several configuration elements
+   * separated by semicolons, e.g.
+   *
+   *   "PROXY host:port; PROXY host2:port2; DIRECT"
+   */
+  set findProxy(String f(Uri url));
+
+  /**
    * Shutdown the HTTP client releasing all resources.
    */
   void shutdown();
 }
 
 
 /**
  * A [HttpClientConnection] is returned by all [HttpClient] methods
  * that initiate a connection to an HTTP server. The handlers will be
  * called as the connection state progresses.
@@ skipping 220 matching lines @@
 class RedirectLimitExceededException extends RedirectException {
   const RedirectLimitExceededException(List<RedirectInfo> redirects)
       : super("Redirect limit exceeded", redirects);
 }
 
 
 class RedirectLoopException extends RedirectException {
   const RedirectLoopException(List<RedirectInfo> redirects)
       : super("Redirect loop detected", redirects);
 }