Make extensions DSE persistent in browser prefs (Reland)

chrome/browser/prefs/session_startup_pref.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_PREFS_SESSION_STARTUP_PREF_H__
 #define CHROME_BROWSER_PREFS_SESSION_STARTUP_PREF_H__
 
 #include <vector>
 
 #include "url/gurl.h"
@@ skipping 18 matching lines @@
 
     // Indicates the user wants to restore a specific set of URLs. The URLs
     // are contained in urls.
     URLS = 3,
   };
 
   // For historical reasons the enum and value registered in the prefs don't
   // 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.
-  static const int kPrefValueLast = 1;
-  static const int kPrefValueURLs = 4;
-  static const int kPrefValueNewTab = 5;
-  static const int kPrefValueMax = 6;
+  enum PrefValue {
+    kPrefValueLast = 1,
+    kPrefValueURLs = 4,
+    kPrefValueNewTab = 5,
+    kPrefValueMax = 6,
+  };
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Returns the default value for |type|.
   static Type GetDefaultStartupType();
 
   // What should happen on startup for the specified profile.
   static void SetStartupPref(Profile* profile, const SessionStartupPref& pref);
   static void SetStartupPref(PrefService* prefs,
                              const SessionStartupPref& pref);
@@ skipping 17 matching lines @@
   ~SessionStartupPref();
 
   // What to do on startup.
   Type type;
 
   // The URLs to restore. Only used if type == URLS.
   std::vector<GURL> urls;
 };
 
 #endif  // CHROME_BROWSER_PREFS_SESSION_STARTUP_PREF_H__