Support automatic javascript test registry in gtest when creating WebUI tests.

chrome/test/data/webui/print_preview.js

 // Copyright (c) 2011 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.
 
 (function() {
    function MockHandler() {
      this.__proto__ = MockHandler.prototype;
    };
 
    MockHandler.prototype = {
@@ skipping 54 matching lines @@
      }
    };
 
    function verifyBasicPrintPreviewButtons(printEnabled) {
      var printButton = $('print-button');
      assertTrue(printButton != null);
      var cancelButton = $('cancel-button');
      assertTrue(cancelButton != null);
    };
 
-   registerCallbacks();
+   if ('window' in this && 'registerCallbacks' in window)
+     registerCallbacks();
 
    internal = {
      'verifyBasicPrintPreviewButtons': verifyBasicPrintPreviewButtons,
    };
  })();
 
 // Tests.
 function testPrintPreview(printEnabled) {
   internal.verifyBasicPrintPreviewButtons(printEnabled);
   var printer_list = $('printer-list');
   assertTrue(printEnabled);
   assertTrue(printer_list.options.length >= 2);
   assertEquals('FooName', printer_list.options[0].text);
   assertEquals('FooDevice', printer_list.options[0].value);
   assertEquals('BarName', printer_list.options[1].text);
   assertEquals('BarDevice', printer_list.options[1].value);
 }