Remove old default search preferences.

ios/chrome/browser/prefs/ios_chrome_pref_service_factory.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 "ios/chrome/browser/prefs/ios_chrome_pref_service_factory.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "components/prefs/json_pref_store.h"
 #include "components/prefs/persistent_pref_store.h"
 #include "components/prefs/pref_filter.h"
 #include "components/prefs/pref_service.h"
 #include "components/proxy_config/proxy_config_pref_names.h"
-#include "components/search_engines/default_search_pref_migration.h"
 #include "components/sync_preferences/pref_service_syncable.h"
 #include "components/sync_preferences/pref_service_syncable_factory.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/prefs/ios_chrome_pref_model_associator_client.h"
 
 namespace {
 
 const char kPreferencesFilename[] = "Preferences";
 
 // Record PersistentPrefStore's reading errors distribution.
@@ skipping 33 matching lines @@
   // chrome_prefs::CreateProfilePrefs uses ProfilePrefStoreManager to create
   // the preference store however since Chrome on iOS does not need to track
   // preference modifications (as applications are sand-boxed), it can use a
   // simple JsonPrefStore to store them (which is what PrefStoreManager uses
   // on platforms that do not track preference modifications).
   sync_preferences::PrefServiceSyncableFactory factory;
   PrepareFactory(&factory, browser_state_path.Append(kPreferencesFilename),
                  pref_io_task_runner);
   std::unique_ptr<sync_preferences::PrefServiceSyncable> pref_service =
       factory.CreateSyncable(pref_registry.get());
-  ConfigureDefaultSearchPrefMigrationToDictionaryValue(pref_service.get());
   return pref_service;
 }
 
 std::unique_ptr<sync_preferences::PrefServiceSyncable>
 CreateIncognitoBrowserStatePrefs(
     sync_preferences::PrefServiceSyncable* pref_service) {
   // List of keys that cannot be changed in the user prefs file by the incognito
   // browser state. All preferences that store information about the browsing
   // history or behaviour of the user should have this property.
   std::vector<const char*> overlay_pref_names;
   overlay_pref_names.push_back(proxy_config::prefs::kProxy);
   return base::WrapUnique(pref_service->CreateIncognitoPrefService(
       nullptr,  // incognito_extension_pref_store
       overlay_pref_names));
 }