Expect two tabs in StartupSupervisedUserProfile test on Windows 10.

chrome/browser/ui/startup/startup_browser_creator_browsertest.cc

 // Copyright (c) 2012 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.
 
 #include <algorithm>
 #include <string>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/prefs/pref_service.h"
@@ skipping 1169 matching lines @@
       content::NOTIFICATION_LOAD_STOP,
       content::NotificationService::AllSources());
   ASSERT_TRUE(launch.Launch(browser()->profile(), std::vector<GURL>(), false,
                             browser()->host_desktop_type()));
 
   // This should have created a new browser window.
   Browser* new_browser = FindOneOtherBrowser(browser());
   ASSERT_TRUE(new_browser);
 
   TabStripModel* tab_strip = new_browser->tab_strip_model();
-  // There should be only one tab.
-  EXPECT_EQ(1, tab_strip->count());
+  // There should be only one tab, except on Windows 10. See crbug.com/505029.
+  const int tab_count = IsWindows10OrNewer() ? 2 : 1;
+  EXPECT_EQ(tab_count, tab_strip->count());
 }
 
 #endif  // !defined(OS_CHROMEOS)
 
 // These tests are not applicable to Chrome OS as neither master_preferences nor
 // the sync promo exist there.
 #if !defined(OS_CHROMEOS)
 
 // On a branded Linux build, policy is required to suppress the first-run
 // dialog.
@@ skipping 423 matching lines @@
   ASSERT_EQ(1, tab_strip->count());
   EXPECT_EQ("title1.html",
             tab_strip->GetWebContentsAt(0)->GetURL().ExtractFileName());
 }
 #endif  // defined(ENABLE_CONFIGURATION_POLICY)
 
 #endif  // !defined(OS_LINUX) || !defined(GOOGLE_CHROME_BUILD) ||
         // defined(ENABLE_CONFIGURATION_POLICY)
 
 #endif  // !defined(OS_CHROMEOS)