Do not CreateSentinel until after the process singleton has been grabbed by the current process.

chrome/browser/sessions/session_restore_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 "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/process/launch.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 72 matching lines @@
           SessionServiceFactory::GetForProfile(browser()->profile()));
       helper.SetForceBrowserNotAliveWithNoWindows(true);
       helper.ReleaseService();
     }
 #endif
 
     InProcessBrowserTest::SetUpOnMainThread();
   }
 
   virtual bool SetUpUserDataDirectory() OVERRIDE {
-    // Make sure the first run sentinel file exists before running these tests,
-    // since some of them customize the session startup pref whose value can
-    // be different than the default during the first run.
-    // TODO(bauerb): set the first run flag instead of creating a sentinel file.
-    first_run::CreateSentinel();
-
     url1_ = ui_test_utils::GetTestUrl(
         base::FilePath().AppendASCII("session_history"),
         base::FilePath().AppendASCII("bot1.html"));
     url2_ = ui_test_utils::GetTestUrl(
         base::FilePath().AppendASCII("session_history"),
         base::FilePath().AppendASCII("bot2.html"));
     url3_ = ui_test_utils::GetTestUrl(
         base::FilePath().AppendASCII("session_history"),
         base::FilePath().AppendASCII("bot3.html"));
 
@@ skipping 1020 matching lines @@
   content::NavigationController* controller =
       &browser()->tab_strip_model()->GetActiveWebContents()->GetController();
   EXPECT_TRUE(
       controller->GetDefaultSessionStorageNamespace()->should_persist());
 
   // Quit and restore. Check that no extra tabs were created.
   Browser* new_browser = QuitBrowserAndRestore(browser(), 1);
   ASSERT_EQ(1u, active_browser_list_->size());
   EXPECT_EQ(1, new_browser->tab_strip_model()->count());
 }