Add support for multiple HTTP proxies

tests/standalone/io/http_proxy_test.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.
 
 #import("dart:io");
 #import("dart:uri");
 
 class Server {
   HttpServer server;
   int proxyHops;
+  List<String> directRequestPaths;
   int requestCount = 0;
 
-  Server(this.proxyHops) : server = new HttpServer();
+  Server(this.proxyHops, this.directRequestPaths) : server = new HttpServer();
 
   void start() {
     server.listen("127.0.0.1", 0);
     server.defaultRequestHandler =
         (HttpRequest request, HttpResponse response) {
           requestCount++;
-          if (proxyHops > 0) {
+          // Check whether a proxy or direct connection is expected.
+          bool direct = directRequestPaths.reduce(
+              false,
+              (prev, path) => prev ? prev : path == request.path);
+          if (!direct && proxyHops > 0) {
             Expect.isNotNull(request.headers[HttpHeaders.VIA]);
             Expect.equals(1, request.headers[HttpHeaders.VIA].length);
             Expect.equals(
                 proxyHops,
                 request.headers[HttpHeaders.VIA][0].split(",").length);
           } else {
             Expect.isNull(request.headers[HttpHeaders.VIA]);
           }
           StringInputStream stream = new StringInputStream(request.inputStream);
           StringBuffer body = new StringBuffer();
           stream.onData = () => body.add(stream.read());
           stream.onClosed = () {
             String path = request.path.substring(1);
             String content = "$path$path$path";
             Expect.equals(content, body.toString());
             response.outputStream.writeString(request.path);
             response.outputStream.close();
           };
         };
   }
 
   void shutdown() {
     server.close();
   }
 
   int get port => server.port;
 }
 
-Server setupServer(int proxyHops) {
-  Server server = new Server(proxyHops);
+Server setupServer(int proxyHops,
+                   [List<String> directRequestPaths = const <String>[]]) {
+  Server server = new Server(proxyHops, directRequestPaths);
   server.start();
   return server;
 }
 
 class ProxyServer {
   HttpServer server;
   HttpClient client;
   int requestCount = 0;
 
   ProxyServer() : server = new HttpServer(), client = new HttpClient();
@@ skipping 97 matching lines @@
           client.shutdown();
         }
       };
     };
   }
 }
 
 int testProxyDoneCount = 0;
 void testProxy() {
   ProxyServer proxyServer = setupProxyServer();
-  Server server = setupServer(1);
+  Server server = setupServer(1, ["/4"]);
   HttpClient client = new HttpClient();
 
   List<String> proxy =
       ["PROXY localhost:${proxyServer.port}",
        "PROXY localhost:${proxyServer.port}; PROXY hede.hule.hest:8080",
+       "PROXY hede.hule.hest:8080; PROXY localhost:${proxyServer.port}",
+       "PROXY hede.hule.hest:8080; PROXY hede.hule.hest:8181; PROXY localhost:${proxyServer.port}",
+       "PROXY hede.hule.hest:8080; PROXY hede.hule.hest:8181; DIRECT",
        "PROXY localhost:${proxyServer.port}; DIRECT"];
 
   client.findProxy = (Uri uri) {
     // Pick the proxy configuration based on the request path.
     int index = int.parse(uri.path.substring(1));
     return proxy[index];
   };
 
   for (int i = 0; i < proxy.length; i++) {
     HttpClientConnection conn =
@@ skipping 19 matching lines @@
   }
 }
 
 int testProxyChainDoneCount = 0;
 void testProxyChain() {
   // Setup two proxy servers having the first using the second as its proxy.
   ProxyServer proxyServer1 = setupProxyServer();
   ProxyServer proxyServer2 = setupProxyServer();
   proxyServer1.client.findProxy = (_) => "PROXY 127.0.0.1:${proxyServer2.port}";
 
-  Server server = setupServer(2);
+  Server server = setupServer(2, ["/4"]);
   HttpClient client = new HttpClient();
 
   List<String> proxy =
       ["PROXY localhost:${proxyServer1.port}",
        "PROXY localhost:${proxyServer1.port}; PROXY hede.hule.hest:8080",
+       "PROXY hede.hule.hest:8080; PROXY localhost:${proxyServer1.port}",
+       "PROXY hede.hule.hest:8080; PROXY hede.hule.hest:8181; PROXY localhost:${proxyServer1.port}",
+       "PROXY hede.hule.hest:8080; PROXY hede.hule.hest:8181; DIRECT",
        "PROXY localhost:${proxyServer1.port}; DIRECT"];
 
   client.findProxy = (Uri uri) {
     // Pick the proxy configuration based on the request path.
     int index = int.parse(uri.path.substring(1));
     return proxy[index];
   };
 
   for (int i = 0; i < proxy.length; i++) {
     HttpClientConnection conn =
@@ skipping 21 matching lines @@
 }
 
 int testRealProxyDoneCount = 0;
 void testRealProxy() {
   Server server = setupServer(1);
   HttpClient client = new HttpClient();
 
   List<String> proxy =
       ["PROXY localhost:8080",
        "PROXY localhost:8080; PROXY hede.hule.hest:8080",
+       "PROXY hede.hule.hest:8080; PROXY localhost:8080",
        "PROXY localhost:8080; DIRECT"];
 
   client.findProxy = (Uri uri) {
     // Pick the proxy configuration based on the request path.
     int index = int.parse(uri.path.substring(1));
     return proxy[index];
   };
 
   for (int i = 0; i < proxy.length; i++) {
     HttpClientConnection conn =
@@ skipping 20 matching lines @@
 
 main() {
   testInvalidProxy();
   testDirectProxy();
   testProxy();
   testProxyChain();
   // This test is not normally run. It can be used for locally testing
   // with a real proxy server (e.g. Apache).
   // testRealProxy();
 }