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

chrome/browser/sessions/session_restore_browsertest.cc

Index: chrome/browser/sessions/session_restore_browsertest.cc
diff --git a/chrome/browser/sessions/session_restore_browsertest.cc b/chrome/browser/sessions/session_restore_browsertest.cc
index ba9fe9d622040d654e7e93bb7165a2cfb30516a3..512683a76379ebd97911a59fb2c3780f2932cf6b 100644
--- a/chrome/browser/sessions/session_restore_browsertest.cc
+++ b/chrome/browser/sessions/session_restore_browsertest.cc
@@ -90,12 +90,6 @@ class SessionRestoreTest : public InProcessBrowserTest {
   }
 
   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"));