[Offline pages] Add new Error page failure status inside the MHTML archiver and update correspondin…

components/offline_pages/core/offline_page_types.h

Index: components/offline_pages/core/offline_page_types.h
diff --git a/components/offline_pages/core/offline_page_types.h b/components/offline_pages/core/offline_page_types.h
index ae9e298af8e6a1fd1287995f1f92c311ac5b3262..13dfbab91d2b4ae091735f1e87e5a945dd13be97 100644
--- a/components/offline_pages/core/offline_page_types.h
+++ b/components/offline_pages/core/offline_page_types.h
@@ -34,6 +34,8 @@ enum class SavePageResult {
   // are already locally accessible.
   SKIPPED,
   SECURITY_CERTIFICATE_ERROR,
+  // Returned when we detect trying to save a chrome error page.
+  ERROR_PAGE_DETECTED,
   // NOTE: always keep this entry at the end. Add new result types only
   // immediately above this line. Make sure to update the corresponding
   // histogram enum accordingly.