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

chrome/browser/first_run/first_run.h

Index: chrome/browser/first_run/first_run.h
diff --git a/chrome/browser/first_run/first_run.h b/chrome/browser/first_run/first_run.h
index 4d1628c4427f9d029c602aff73cdf19f3944dd4b..a548bbf41a7658367ecc705e0c7f5d2e232b362c 100644
--- a/chrome/browser/first_run/first_run.h
+++ b/chrome/browser/first_run/first_run.h
@@ -91,8 +91,10 @@ struct MasterPrefs {
 // 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();