Offline Pages: Replace Observer::OfflinePageModelChanged with OfflinePageAdded.

components/offline_pages/core/offline_page_model.h

Index: components/offline_pages/core/offline_page_model.h
diff --git a/components/offline_pages/core/offline_page_model.h b/components/offline_pages/core/offline_page_model.h
index 58f60e0033eeb100b1bc58f11c4ecbcb2b24b9d9..584d81a9566c1e73eea61ba90600c5b4a2c8864b 100644
--- a/components/offline_pages/core/offline_page_model.h
+++ b/components/offline_pages/core/offline_page_model.h
@@ -78,9 +78,9 @@ class OfflinePageModel : public base::SupportsUserData {
     // Invoked when the model has finished loading.
     virtual void OfflinePageModelLoaded(OfflinePageModel* model) = 0;
 
-    // Invoked when the model is being updated, due to adding, removing or
-    // updating an offline page.
-    virtual void OfflinePageModelChanged(OfflinePageModel* model) = 0;
+    // Invoked when the model is being updated due to adding an offline page.
+    virtual void OfflinePageAdded(OfflinePageModel* model,
+                                  const OfflinePageItem& added_page) = 0;
 
     // Invoked when an offline copy related to |offline_id| was deleted.
     virtual void OfflinePageDeleted(int64_t offline_id,