Fix homepage migration for users who never changed their settings.

chrome/common/pref_names.cc

 // 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.
 
 #include "chrome/common/pref_names.h"
 
 #include "base/basictypes.h"
 
 namespace prefs {
 
@@ skipping 25 matching lines @@
 
 // Does this user have a Google+ Profile?
 const char kIsGooglePlusUser[] = "is_google_plus_user";
 
 // Used to determine if the last session exited cleanly. Set to false when
 // first opened, and to true when closing. On startup if the value is false,
 // it means the profile didn't exit cleanly.
 const char kSessionExitedCleanly[] = "profile.exited_cleanly";
 
 // An integer pref. Holds one of several values:
-// 0: (or empty) don't do anything special on startup.
+// 0: (deprecated) open the homepage on startup
 // 1: restore the last session.
 // 2: this was used to indicate a specific session should be restored. It is
 //    no longer used, but saved to avoid conflict with old preferences.
 // 3: unused, previously indicated the user wants to restore a saved session.
 // 4: restore the URLs defined in kURLsToRestoreOnStartup.
+// 5: open the New Tab Page on startup
 const char kRestoreOnStartup[] = "session.restore_on_startup";
 
 // The URLs to restore on startup or when the home button is pressed. The URLs
 // are only restored on startup if kRestoreOnStartup is 4.
 const char kURLsToRestoreOnStartup[] = "session.urls_to_restore_on_startup";
 
+// A preference to keep track of whether we have already checked whether we
+// need to migrate the user from kRestoreOnStartup=0 to kRestoreOnStartup=4.
+// We only need to do this check once, on upgrade from m18 or lower to m19 or
+// higher.
+const char kRestoreOnStartupMigrated[] = "session.restore_on_startup_migrated";
+
 // The application locale.
 // For OS_CHROMEOS we maintain kApplicationLocale property in both local state
 // and user's profile.  Global property determines locale of login screen,
 // while user's profile determines his personal locale preference.
 const char kApplicationLocale[] = "intl.app_locale";
 #if defined(OS_CHROMEOS)
 // Locale preference of device' owner.  ChromeOS device appears in this locale
 // after startup/wakeup/signout.
 const char kOwnerLocale[] = "intl.owner_locale";
 // Locale accepted by user.  Non-syncable.
@@ skipping 1767 matching lines @@
 const char kRailBreakProportion[] =
     "gesture.rail_break_proportion";
 const char kRailStartProportion[] =
     "gesture.rail_start_proportion";
 #endif
 
 // Indicates whether the browser is in managed mode.
 const char kInManagedMode[] = "managed_mode";
 
 }  // namespace prefs