Remove year+ old migration support of "session.urls_to_restore_on_startup".

chrome/browser/prefs/chrome_pref_model_associator_client.cc

 // Copyright 2015 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/browser/prefs/chrome_pref_model_associator_client.h"
 
 #include "base/memory/singleton.h"
 #include "chrome/common/pref_names.h"
 #include "components/content_settings/core/browser/website_settings_info.h"
 #include "components/content_settings/core/browser/website_settings_registry.h"
 
-namespace {
-// List of migrated preference name pairs. If a preference is migrated
-// (meaning renamed) adding the old and new preference names here will ensure
-// that the sync engine knows how to deal with the synced values coming in
-// with the old name. Preference migration itself doesn't happen here. It may
-// happen in session_startup_pref.cc.
-const struct MigratedPreferences {
-  const char* const old_name;
-  const char* const new_name;
-} kMigratedPreferences[] = {
-    {prefs::kURLsToRestoreOnStartupOld, prefs::kURLsToRestoreOnStartup},
-};
-}  // namespace
-
 // static
 ChromePrefModelAssociatorClient*
 ChromePrefModelAssociatorClient::GetInstance() {
   return base::Singleton<ChromePrefModelAssociatorClient>::get();
 }
 
 ChromePrefModelAssociatorClient::ChromePrefModelAssociatorClient() {}
 
 ChromePrefModelAssociatorClient::~ChromePrefModelAssociatorClient() {}
 
 bool ChromePrefModelAssociatorClient::IsMergeableListPreference(
     const std::string& pref_name) const {
   return pref_name == prefs::kURLsToRestoreOnStartup;
 }
 
 bool ChromePrefModelAssociatorClient::IsMergeableDictionaryPreference(
     const std::string& pref_name) const {
   const content_settings::WebsiteSettingsRegistry& registry =
       *content_settings::WebsiteSettingsRegistry::GetInstance();
   for (const content_settings::WebsiteSettingsInfo* info : registry) {
     if (info->pref_name() == pref_name)
       return true;
   }
   return false;
 }
-
-bool ChromePrefModelAssociatorClient::IsMigratedPreference(
-    const std::string& new_pref_name,
-    std::string* old_pref_name) const {
-  for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
-    if (new_pref_name == kMigratedPreferences[i].new_name) {
-      old_pref_name->assign(kMigratedPreferences[i].old_name);
-      return true;
-    }
-  }
-  return false;
-}
-
-bool ChromePrefModelAssociatorClient::IsOldMigratedPreference(
-    const std::string& old_pref_name,
-    std::string* new_pref_name) const {
-  for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
-    if (old_pref_name == kMigratedPreferences[i].old_name) {
-      new_pref_name->assign(kMigratedPreferences[i].new_name);
-      return true;
-    }
-  }
-  return false;
-}