Fix crash on Linux when a normal window is created after a hidden window.

chrome/test/data/extensions/platform_apps/crashtest_hidden_windows/test.js

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+chrome.app.runtime.onLaunched.addListener(function() {
+  chrome.app.window.create(
+    'index.html', { width: 800, height: 600, hidden: true },
+    function() {
+      chrome.app.window.create(
+        'index.html', { width: 800, height: 600, hidden: false },
+        function() {
+          chrome.test.sendMessage("Done");
+        }
+      );
+    }
+  );
+});