Offline Pages: Replace Observer::OfflinePageModelChanged with OfflinePageAdded.

components/offline_pages/offline_page_model_impl.cc

Index: components/offline_pages/offline_page_model_impl.cc
diff --git a/components/offline_pages/offline_page_model_impl.cc b/components/offline_pages/offline_page_model_impl.cc
index 577dd26082d8e6984fbfcf1c5a1afeda6ae89955..bfc1f0deecd1f7186a6f2c6576ebe13685eacfbe 100644
--- a/components/offline_pages/offline_page_model_impl.cc
+++ b/components/offline_pages/offline_page_model_impl.cc
@@ -768,6 +768,7 @@ void OfflinePageModelImpl::OnAddOfflinePageDone(
     const OfflinePageItem& offline_page,
     ItemActionStatus status) {
   SavePageResult result;
+
   if (status == ItemActionStatus::SUCCESS) {
     offline_pages_[offline_page.offline_id] = offline_page;
     result = SavePageResult::SUCCESS;
@@ -790,8 +791,11 @@ void OfflinePageModelImpl::OnAddOfflinePageDone(
   }
 
   DeletePendingArchiver(archiver);
-  for (Observer& observer : observers_)
-    observer.OfflinePageModelChanged(this);
+  for (Observer& observer : observers_) {
+    observer.OfflinePageAdded(this, result, result == SavePageResult::SUCCESS
+                                                ? &offline_page
+                                                : nullptr);
+  }
 }
 
 void OfflinePageModelImpl::OnMarkPageAccesseDone(