Add Store+Sync to reading list.

ios/chrome/browser/reading_list/reading_list_model_observer.h

Index: ios/chrome/browser/reading_list/reading_list_model_observer.h
diff --git a/ios/chrome/browser/reading_list/reading_list_model_observer.h b/ios/chrome/browser/reading_list/reading_list_model_observer.h
index 1d7bea850fcdda8a8cbaa1a343aed2ed82ebbc84..f08d35dfdb74e489e45238d56cbc8e13da3a8072 100644
--- a/ios/chrome/browser/reading_list/reading_list_model_observer.h
+++ b/ios/chrome/browser/reading_list/reading_list_model_observer.h
@@ -41,10 +41,11 @@ class ReadingListModelObserver {
   virtual void ReadingListWillRemoveReadEntry(const ReadingListModel* model,
                                               size_t index) {}
   // Invoked when elements are moved from unread to read or from read to unread.
-  // |index| is the original position in the origin list. The element will be
-  // added to the beginning of the target list.
+  // |index| is the original position  and |read| the origin status. The element
+  // will change list and/or index but will not be deleted.
   virtual void ReadingListWillMoveEntry(const ReadingListModel* model,
-                                        size_t index) {}
+                                        size_t index,
+                                        bool read) {}
 
   // Invoked when elements are added to the read or the unread list. The new
   // entries are always added at the beginning. these methods may be called