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

chrome/browser/first_run/first_run.h

 // 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.
 
 #ifndef CHROME_BROWSER_FIRST_RUN_FIRST_RUN_H_
 #define CHROME_BROWSER_FIRST_RUN_FIRST_RUN_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 73 matching lines @@
   std::vector<GURL> new_tabs;
   std::vector<GURL> bookmarks;
   std::string import_bookmarks_path;
   std::string variations_seed;
   std::string suppress_default_browser_prompt_for_version;
 };
 
 // Returns true if this is the first time chrome is run for this user.
 bool IsChromeFirstRun();
 
-// Creates the sentinel file that signals that chrome has been configured.
-bool CreateSentinel();
+// Creates the first run sentinel if needed. This should only be called after
+// the process singleton has been grabbed by the current process
+// (http://crbug.com/264694).
+void CreateSentinelIfNeeded();
 
 // Get RLZ ping delay pref name.
 std::string GetPingDelayPrefName();
 
 // Register user preferences used by the MasterPrefs structure.
 void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
 // Removes the sentinel file created in ConfigDone(). Returns false if the
 // sentinel file could not be removed.
 bool RemoveSentinel();
@@ skipping 86 matching lines @@
                        const content::NotificationDetails& details) OVERRIDE;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(FirstRunBubbleLauncher);
 };
 
 }  // namespace first_run
 
 #endif  // CHROME_BROWSER_FIRST_RUN_FIRST_RUN_H_