Fix the Download Notifications for Offline Pages to indicate bytes loaded.

components/offline_pages/core/background/offliner_stub.h

Index: components/offline_pages/core/background/offliner_stub.h
diff --git a/components/offline_pages/core/background/offliner_stub.h b/components/offline_pages/core/background/offliner_stub.h
index 821f5ea9ed5f10acc164a13ab4a49c170cfce4a7..61c9d9582930a427f291c891e99482ce194d28f3 100644
--- a/components/offline_pages/core/background/offliner_stub.h
+++ b/components/offline_pages/core/background/offliner_stub.h
@@ -17,7 +17,8 @@ class OfflinerStub : public Offliner {
   ~OfflinerStub() override;
 
   bool LoadAndSave(const SavePageRequest& request,
-                   const CompletionCallback& callback) override;
+                   const CompletionCallback& completion_callback,
+                   const ProgressCallback& progress_callback) override;
 
   void Cancel() override;
 
@@ -34,7 +35,8 @@ class OfflinerStub : public Offliner {
   void enable_snapshot_on_last_retry() { snapshot_on_last_retry_ = true; }
 
  private:
-  CompletionCallback callback_;
+  CompletionCallback completion_callback_;
+  ProgressCallback progress_callback_;
   bool disable_loading_;
   bool enable_callback_;
   bool cancel_called_;