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

components/offline_pages/core/background/request_notifier.h

Index: components/offline_pages/core/background/request_notifier.h
diff --git a/components/offline_pages/core/background/request_notifier.h b/components/offline_pages/core/background/request_notifier.h
index ef3c62f69f7861803b24a4fceae854e0bb5f27a3..95fbb09f3cda876a1b209149efdc09e27c6991c6 100644
--- a/components/offline_pages/core/background/request_notifier.h
+++ b/components/offline_pages/core/background/request_notifier.h
@@ -38,6 +38,11 @@ class RequestNotifier {
 
   // Notifies observers that |request| has been changed.
   virtual void NotifyChanged(const SavePageRequest& request) = 0;
+
+  // Notifies observers of progress on |request|, which received
+  // |received_bytes| at that point.
+  virtual void NotifyNetworkProgress(const SavePageRequest& request,
+                                     int64_t received_bytes) = 0;
 };
 
 }  // namespace offline_pages