Change backlog on http server listen from 5 to 128.

runtime/bin/http_impl.dart

Index: runtime/bin/http_impl.dart
diff --git a/runtime/bin/http_impl.dart b/runtime/bin/http_impl.dart
index 9b9a46d1f79b1662d4c1a691cb62c6dd49b5468e..0f5a63f6fc09223dd1acf1d37b827d7b30e72971 100644
--- a/runtime/bin/http_impl.dart
+++ b/runtime/bin/http_impl.dart
@@ -1432,7 +1432,7 @@ class _HttpServer implements HttpServer {
   _HttpServer() : _connections = new Set<_HttpConnection>(),
                   _handlers = new List<_RequestHandlerRegistration>();
 
-  void listen(String host, int port, [int backlog = 5]) {
+  void listen(String host, int port, [int backlog = 128]) {
     listenOn(new ServerSocket(host, port, backlog));
     _closeServer = true;
   }