Attempt to make probability of test flake in tests/standalone/io/socket_bind_test lower

tests/standalone/io/socket_bind_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.
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:convert';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
@@ skipping 48 matching lines @@
     });
   });
 }
 
 Future testBindDifferentAddresses(InternetAddress addr1,
                                   InternetAddress addr2,
                                   bool addr1V6Only,
                                   bool addr2V6Only) async {
   int freePort = await freeIPv4AndIPv6Port();
 
-  asyncStart();
-  return ServerSocket.bind(
-      addr1, freePort, v6Only: addr1V6Only, shared: false).then((socket) {
+  var socket = await ServerSocket.bind(
+      addr1, freePort, v6Only: addr1V6Only, shared: false);
+
+  try {
     Expect.isTrue(socket.port > 0);
 
-    asyncStart();
-    return ServerSocket.bind(
-        addr2, freePort, v6Only: addr2V6Only, shared: false).then((socket2) {
+    var socket2 = await ServerSocket.bind(
+        addr2, freePort, v6Only: addr2V6Only, shared: false);
+    try {
       Expect.equals(socket.port, socket2.port);
-
-      return Future.wait([
-          socket.close().whenComplete(asyncEnd),
-          socket2.close().whenComplete(asyncEnd),
-      ]);
-    });
-  });
+    } finally {
+      await socket2.close();
+    }
+  } finally {
+    await socket.close();
+  }
 }
 
 testListenCloseListenClose(String host) async {
   asyncStart();
 
   ServerSocket socket =
       await ServerSocket.bind(host, 0, shared: true);
   ServerSocket socket2 =
       await ServerSocket.bind(host, socket.port, shared: true);
 
@@ skipping 18 matching lines @@
 }
 
 Future<int> freeIPv4AndIPv6Port() async {
   var socket =
     await ServerSocket.bind(InternetAddress.ANY_IP_V6, 0, v6Only: false);
   int port = socket.port;
   await socket.close();
   return port;
 }
 
+Future retry(Future fun(), {int maxCount: 10}) async {
+  for (int i = 0; i < maxCount; i++) {
+    try {
+      // If there is no exception this will simply return, otherwise we keep
+      // trying.
+      return await fun();
+    } catch (_) {}
+    print("Failed to execute test closure in attempt $i "
+          "(${maxCount - i} retries left).");
+  }
+  return await fun();
+}
+
 main() async {
   asyncStart();
-  await testBindDifferentAddresses(InternetAddress.ANY_IP_V6,
-                                   InternetAddress.ANY_IP_V4,
-                                   true,
-                                   false);
-  await testBindDifferentAddresses(InternetAddress.ANY_IP_V4,
-                                   InternetAddress.ANY_IP_V6,
-                                   false,
-                                   true);
+
+  await retry(() async {
+    await testBindDifferentAddresses(InternetAddress.ANY_IP_V6,
+                                     InternetAddress.ANY_IP_V4,
+                                     true,
+                                     false);
+  });
+  await retry(() async {
+    await testBindDifferentAddresses(InternetAddress.ANY_IP_V4,
+                                     InternetAddress.ANY_IP_V6,
+                                     false,
+                                     true);
+  });
 
   for (var host in ['127.0.0.1', '::1']) {
     testBindShared(host, false);
     testBindShared(host, true);
 
     negTestBindSharedMismatch(host, false);
     negTestBindSharedMismatch(host, true);
 
     negTestBindV6OnlyMismatch(host, true);
     negTestBindV6OnlyMismatch(host, false);
 
     testListenCloseListenClose(host);
   }
   asyncEnd();
 }