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

chrome/browser/ui/cocoa/first_run_dialog.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/first_run_dialog.h"
 
 #include "base/bind.h"
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #import "base/mac/scoped_nsobject.h"
@@ skipping 103 matching lines @@
     BOOL make_default_browser = [dialog.get() makeDefaultBrowser];
     if (make_default_browser) {
       bool success = ShellIntegration::SetAsDefaultBrowser();
       DCHECK(success);
     }
   }
 #else  // GOOGLE_CHROME_BUILD
   // We don't show the dialog in Chromium.
 #endif  // GOOGLE_CHROME_BUILD
 
-  first_run::CreateSentinel();
-
   // Set preference to show first run bubble and welcome page.
   // Only display the bubble if there is a default search provider.
   TemplateURLService* search_engines_model =
       TemplateURLServiceFactory::GetForProfile(profile);
   if (search_engines_model &&
       search_engines_model->GetDefaultSearchProvider()) {
     first_run::SetShowFirstRunBubblePref(first_run::FIRST_RUN_BUBBLE_SHOW);
   }
   first_run::SetShouldShowWelcomePage();
 
@@ skipping 155 matching lines @@
   [NSApp stopModal];
 }
 
 - (IBAction)learnMore:(id)sender {
   NSString* urlStr = base::SysUTF8ToNSString(chrome::kLearnMoreReportingURL);
   NSURL* learnMoreUrl = [NSURL URLWithString:urlStr];
   [[NSWorkspace sharedWorkspace] openURL:learnMoreUrl];
 }
 
 @end