Store the "browser autorestarted, last session must be restored" information in a preference.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index eaee7c8495147801f4cc636a61a5957ee9923992..6743d18f0604382460504c59de319ed936a76d53 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1201,6 +1201,9 @@ const char kShutdownNumProcessesSlow[] = "shutdown.num_processes_slow";
 // before shutting everything down.
 const char kRestartLastSessionOnShutdown[] = "restart.last.session.on.shutdown";
 
+// Set before autorestarting Chrome, cleared on clean exit.
+const char kWasRestarted[] = "was.restarted";
+
 // Number of bookmarks/folders on the bookmark bar/other bookmark folder.
 const char kNumBookmarksOnBookmarkBar[] =
     "user_experience_metrics.num_bookmarks_on_bookmark_bar";