Add Store+Sync to reading list.

ios/chrome/browser/reading_list/reading_list_model_factory.h

Index: ios/chrome/browser/reading_list/reading_list_model_factory.h
diff --git a/ios/chrome/browser/reading_list/reading_list_model_factory.h b/ios/chrome/browser/reading_list/reading_list_model_factory.h
index e76639132c84adcf48da3251cf6f6aa288ca6b7a..7a97a443f9df4319ce0a260adb233c04553db846 100644
--- a/ios/chrome/browser/reading_list/reading_list_model_factory.h
+++ b/ios/chrome/browser/reading_list/reading_list_model_factory.h
@@ -15,6 +15,7 @@ struct DefaultSingletonTraits;
 }  // namespace base
 
 class ReadingListModel;
+class ReadingListStore;
 
 namespace ios {
 class ChromeBrowserState;
@@ -29,6 +30,7 @@ class ReadingListModelFactory : public BrowserStateKeyedServiceFactory {
   static ReadingListModel* GetForBrowserStateIfExists(
       ios::ChromeBrowserState* browser_state);
   static ReadingListModelFactory* GetInstance();
+  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
  private:
   friend struct base::DefaultSingletonTraits<ReadingListModelFactory>;