Make GetBestPageForOnlineURL async

components/offline_pages/offline_page_model.h

Index: components/offline_pages/offline_page_model.h
diff --git a/components/offline_pages/offline_page_model.h b/components/offline_pages/offline_page_model.h
index 9c6efb7aaca737e960f67ac1ce10672776b32f3a..07aa4ed367ef62744ee2472cf00dd3bdd2b87dc6 100644
--- a/components/offline_pages/offline_page_model.h
+++ b/components/offline_pages/offline_page_model.h
@@ -165,16 +165,6 @@ class OfflinePageModel : public base::SupportsUserData {
       const GURL& online_url,
       const MultipleOfflinePageItemCallback& callback) = 0;
 
-  // Returns via callback an offline page saved for |online_url|, if any. The
-  // best page is chosen based on creation date; a more recently created offline
-  // page will be preferred over an older one. This API function does not
-  // respect namespaces, as it is used to choose which page is rendered in a
-  // tab. Today all namespaces are treated equally for the purposes of this
-  // selection.
-  virtual void GetBestPageForOnlineURL(
-      const GURL& online_url,
-      const SingleOfflinePageItemCallback callback) = 0;
-
   // Returns an offline page saved for |online_url|. A nullptr is returned if
   // not found.  See |GetBestPageForOnlineURL| for selection criteria.
   virtual const OfflinePageItem* MaybeGetBestPageForOnlineURL(