Set unseen state of reading list before notifying observers.

ios/chrome/browser/reading_list/reading_list_model_memory.cc

Index: ios/chrome/browser/reading_list/reading_list_model_memory.cc
diff --git a/ios/chrome/browser/reading_list/reading_list_model_memory.cc b/ios/chrome/browser/reading_list/reading_list_model_memory.cc
index 40f9224b57dabcccfe691912f960d2bebb7bde27..d5ff9794c0fb32017df0dfdbbf2dfbcede513d78 100644
--- a/ios/chrome/browser/reading_list/reading_list_model_memory.cc
+++ b/ios/chrome/browser/reading_list/reading_list_model_memory.cc
@@ -88,10 +88,10 @@ const ReadingListEntry& ReadingListModelMemory::AddEntry(
   FOR_EACH_OBSERVER(ReadingListModelObserver, observers_,
                     ReadingListWillAddUnreadEntry(this, entry));
   unread_.insert(unread_.begin(), entry);
+  hasUnseen_ = true;
   FOR_EACH_OBSERVER(ReadingListModelObserver, observers_,
                     ReadingListDidApplyChanges(this));
 
-  hasUnseen_ = true;
   return *unread_.begin();
 }