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

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 0a7aeec08663caaa04295421c18279985cf68cdc..209c9deec6a2ac5cb70789a4d15da3ae8fd3af2a 100644
--- a/chrome/browser/prefs/session_startup_pref.h
+++ b/chrome/browser/prefs/session_startup_pref.h
@@ -23,9 +23,6 @@ struct SessionStartupPref {
     // Indicates the user wants to open the New Tab page.
     DEFAULT,
 
-    // Deprecated. See comment in session_startup_pref.cc
-    HOMEPAGE,
-
     // Indicates the user wants to restore the last session.
     LAST,
 
@@ -41,7 +38,6 @@ struct SessionStartupPref {
   // 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 kPrefValueHomePage = 0;  // Deprecated

[bartfab (slow), 2015/08/31 15:36:43]

+asvitkine@chromium.org Your advice is needed is needed here. The comment above
reminds us to update histograms.xml. The value 0 is currently documented there
as:

<int value="0" label="Open home page (unused)"/>

Should we remove this entry as it is truly unused now, or should we leave it so
that if some old or misconfigured client does report a value of 0, we can easily
see in the histogram what this used to refer to?

   static const int kPrefValueLast = 1;
   static const int kPrefValueURLs = 4;
   static const int kPrefValueNewTab = 5;
@@ -59,11 +55,6 @@ struct SessionStartupPref {
   static SessionStartupPref GetStartupPref(Profile* profile);
   static SessionStartupPref GetStartupPref(PrefService* prefs);
 
-  // If the user had the "restore on startup" property set to the deprecated
-  // "Open the home page" value, this migrates them to a value that will have
-  // the same effect.
-  static void MigrateIfNecessary(PrefService* prefs);
-
   // Whether the startup type and URLs are managed via policy.
   static bool TypeIsManaged(PrefService* prefs);
   static bool URLsAreManaged(PrefService* prefs);