Remove migration of obsolete value for "session.restore_on_startup".

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 79f06621e38e747718c0db28b39d8a412644b24d..5c6c40bbef997472bd57dc4dcd26508ab010cc06 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -75,12 +75,6 @@ const char kSessionExitType[] = "profile.exit_type";
 // 5: open the New Tab Page on startup.
 const char kRestoreOnStartup[] = "session.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 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.startup_urls";