If MHTML saving is cancelled, delete the page afterwards.

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 8e51e30a26ed8387e6ac007f52f8cdbe82c30b3b..1c70970882d444693d828273914cc5dbc7f26870 100644
--- a/chrome/browser/android/offline_pages/background_loader_offliner.h
+++ b/chrome/browser/android/offline_pages/background_loader_offliner.h
@@ -84,6 +84,9 @@ class BackgroundLoaderOffliner : public Offliner,
   // Called to add a loading signal as we observe it.
   void AddLoadingSignal(const char* signal_name);
 
+  void DeleteOfflinePageCallback(const SavePageRequest& request,
+                                 DeletePageResult result);
+
   std::unique_ptr<background_loader::BackgroundLoaderContents> loader_;
   // Not owned.
   content::BrowserContext* browser_context_;