Revert of Make extensions DSE persistent in browser prefs

chrome/browser/prefs/session_startup_pref.h

Index: chrome/browser/prefs/session_startup_pref.h
diff --git a/chrome/browser/prefs/session_startup_pref.h b/chrome/browser/prefs/session_startup_pref.h
index 81241480c904344636d0ea6efbab734d51554d0f..b13f76d10916699789eb5cd8fdfd21d6e399bad3 100644
--- a/chrome/browser/prefs/session_startup_pref.h
+++ b/chrome/browser/prefs/session_startup_pref.h
@@ -36,12 +36,10 @@
   // line up. These are the values registered in prefs.
   // The values are also recorded in Settings.StartupPageLoadSettings histogram,
   // so make sure to update histograms.xml if you change these.
-  enum PrefValue {
-    kPrefValueLast = 1,
-    kPrefValueURLs = 4,
-    kPrefValueNewTab = 5,
-    kPrefValueMax = 6,
-  };
+  static const int kPrefValueLast = 1;
+  static const int kPrefValueURLs = 4;
+  static const int kPrefValueNewTab = 5;
+  static const int kPrefValueMax = 6;
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);