[protector] Added SessionStartupChange for representing changes in SessionStartupPref.

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__
 #pragma once
 
 #include <vector>
 
@@ skipping 10 matching lines @@
     DEFAULT,
 
     // Deprecated. See comment in session_startup_pref.cc
     HOMEPAGE,
 
     // Indicates the user wants to restore the last session.
     LAST,
 
     // Indicates the user wants to restore a specific set of URLs. The URLs
     // are contained in urls.
-    URLS
+    URLS,
+
+    // Maximum value of this enum.
+    MAX = URLS

[whywhat, 2012/03/11 23:09:33]

Did you mean LAST? :)
You could also use COUNT which doesn't neet to be reassigned to the last one
when another value is added. It's valid though only if the enum is sequential.

[Ivan Korotkov, 2012/03/12 11:20:18]

There is also LAST with a different meaning :) I guess COUNT is ok. Actually, it
wasn't correct to pass MAX to UMA functions...

   };
 
   static void RegisterUserPrefs(PrefService* prefs);
 
   // 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);
   static SessionStartupPref GetStartupPref(Profile* profile);
   static SessionStartupPref GetStartupPref(PrefService* prefs);
@@ skipping 10 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__