Implement correct back-throttleing for web-sockets.

tests/standalone/io/web_socket_ping_test.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 
 
 void testPing(int totalConnections) {
   HttpServer.bind('localhost', 0).then((server) {
+    // The completers will be completed when the pingInterval have terminated
+    // the webSockets.
+    var completers = new List.generate(
+        totalConnections, (_) => new Completer());
+
+    int conns = 0;
     server.transform(new WebSocketTransformer()).listen((webSocket) {
-      webSocket.pingInterval = const Duration(milliseconds: 500);
+      int i = conns++;
+      webSocket.pingInterval = const Duration(milliseconds: 100);
       webSocket.drain();
+      var timer = new Timer.periodic(const Duration(milliseconds: 10), (_) {
+        webSocket.add(new List.filled(10 * 1024, 0));
+      });
+      webSocket.done.then((_) {
+        completers[i].complete();
+        timer.cancel();
+        Expect.equals(WebSocketStatus.GOING_AWAY, webSocket.closeCode);
+        webSocket.close();
+      });
     });
 
     var futures = [];
     for (int i = 0; i < totalConnections; i++) {
       futures.add(
-          WebSocket.connect('ws://localhost:${server.port}').then((webSocket) {
-        webSocket.pingInterval = const Duration(milliseconds: 500);
-        webSocket.drain();
-        new Timer(const Duration(seconds: 2), () {
-          // Should not be closed yet.
-          Expect.equals(null, webSocket.closeCode);
-          webSocket.close();
-        });
-        return webSocket.done;
-      }));
+          WebSocket.connect('ws://localhost:${server.port}')
+              .then((webSocket) {
+                // Don't drain yet, to block data.
+                // Once the server is done, drain the peers.
+                return Future.wait(completers.map((c) => c.future))
+                    .then((_) => webSocket.drain());
+              }));
     }
     Future.wait(futures).then((_) => server.close());
   });
 }
 
 
 void main() {
   testPing(10);
 }