[Offline pages] Update background loader to override the WebContentsObserver methods expected

chrome/browser/android/offline_pages/background_loader_offliner.h

Index: chrome/browser/android/offline_pages/background_loader_offliner.h
diff --git a/chrome/browser/android/offline_pages/background_loader_offliner.h b/chrome/browser/android/offline_pages/background_loader_offliner.h
index 608e88b3006ca0ad23cd68f24e26fb76b6f01961..8d63c3c306e71945fdbae355e8101b06d0fa131a 100644
--- a/chrome/browser/android/offline_pages/background_loader_offliner.h
+++ b/chrome/browser/android/offline_pages/background_loader_offliner.h
@@ -47,8 +47,8 @@ class BackgroundLoaderOffliner : public Offliner,
   bool HandleTimeout(const SavePageRequest& request) override;
 
   // WebContentsObserver implementation.
-  void DocumentLoadedInFrame(content::RenderFrameHost* render_frame) override;
-  void DidStopLoading() override;
+  void DocumentAvailableInMainFrame() override;
+  void DocumentOnLoadCompletedInMainFrame() override;
   void RenderProcessGone(base::TerminationStatus status) override;
   void WebContentsDestroyed() override;
   void DidFinishNavigation(