Enable RL sync by default on iOS

ios/chrome/browser/sync/ios_chrome_sync_client.mm

 // 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/sync/ios_chrome_sync_client.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "components/autofill/core/browser/webdata/autocomplete_syncable_service.h"
 #include "components/autofill/core/browser/webdata/autofill_profile_syncable_service.h"
 #include "components/autofill/core/browser/webdata/autofill_wallet_metadata_syncable_service.h"
 #include "components/autofill/core/browser/webdata/autofill_wallet_syncable_service.h"
 #include "components/autofill/core/browser/webdata/autofill_webdata_service.h"
 #include "components/browser_sync/browser_sync_switches.h"
 #include "components/browser_sync/profile_sync_components_factory_impl.h"
 #include "components/browser_sync/profile_sync_service.h"
 #include "components/dom_distiller/core/dom_distiller_service.h"
 #include "components/history/core/browser/history_model_worker.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/invalidation/impl/profile_invalidation_provider.h"
 #include "components/keyed_service/core/service_access_type.h"
 #include "components/password_manager/core/browser/password_store.h"
 #include "components/password_manager/sync/browser/password_model_worker.h"
-#include "components/reading_list/reading_list_model.h"
+#include "components/reading_list/core/reading_list_switches.h"
+#include "components/reading_list/ios/reading_list_model.h"
 #include "components/search_engines/search_engine_data_type_controller.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/sync/base/extensions_activity.h"
 #include "components/sync/base/report_unrecoverable_error.h"
 #include "components/sync/driver/sync_api_component_factory.h"
 #include "components/sync/driver/sync_util.h"
 #include "components/sync/driver/ui_data_type_controller.h"
 #include "components/sync/engine/browser_thread_model_worker.h"
 #include "components/sync/engine/passive_model_worker.h"
 #include "components/sync/engine/ui_model_worker.h"
@@ skipping 296 matching lines @@
 
 base::WeakPtr<syncer::ModelTypeSyncBridge>
 IOSChromeSyncClient::GetSyncBridgeForModelType(syncer::ModelType type) {
   switch (type) {
     case syncer::DEVICE_INFO:
       return IOSChromeProfileSyncServiceFactory::GetForBrowserState(
                  browser_state_)
           ->GetDeviceInfoSyncBridge()
           ->AsWeakPtr();
     case syncer::READING_LIST: {
+      DCHECK(reading_list::switches::IsReadingListEnabled());
       ReadingListModel* reading_list_model =
           ReadingListModelFactory::GetForBrowserState(browser_state_);
-      if (reading_list_model)
-        return reading_list_model->GetModelTypeSyncBridge()->AsWeakPtr();
-      return base::WeakPtr<syncer::ModelTypeSyncBridge>();
+      return reading_list_model->GetModelTypeSyncBridge()->AsWeakPtr();
     }
     default:
       NOTREACHED();
       return base::WeakPtr<syncer::ModelTypeSyncBridge>();
   }
 }
 
 scoped_refptr<syncer::ModelSafeWorker>
 IOSChromeSyncClient::CreateModelWorkerForGroup(syncer::ModelSafeGroup group) {
   DCHECK_CURRENTLY_ON(web::WebThread::UI);
@@ skipping 52 matching lines @@
         IOSChromeProfileSyncServiceFactory::GetForBrowserState(browser_state);
     if (profile_sync_service != nullptr) {
       const syncer::DeviceInfoTracker* tracker =
           profile_sync_service->GetDeviceInfoTracker();
       if (tracker != nullptr) {
         trackers->push_back(tracker);
       }
     }
   }
 }