[Offline Pages] Feature flag to allow concurrent background loading on svelte

components/offline_pages/offline_page_feature.h

Index: components/offline_pages/offline_page_feature.h
diff --git a/components/offline_pages/offline_page_feature.h b/components/offline_pages/offline_page_feature.h
index 202e6923ec198f2a67ad4c7d8d80ff895d07f682..7ba846cd3fdc72be45b9e1eeb98adae284f55d88 100644
--- a/components/offline_pages/offline_page_feature.h
+++ b/components/offline_pages/offline_page_feature.h
@@ -12,6 +12,7 @@ namespace offline_pages {
 
 extern const base::Feature kOfflineBookmarksFeature;
 extern const base::Feature kOffliningRecentPagesFeature;
+extern const base::Feature kOfflinePagesSvelteConcurrentLoadingFeature;
 extern const base::Feature kOfflinePagesCTFeature;
 extern const base::Feature kOfflinePagesSharingFeature;
 extern const base::Feature kBackgroundLoaderForDownloadsFeature;
@@ -33,6 +34,9 @@ bool IsOfflinePagesSharingEnabled();
 // background scheduler is enabled.
 bool IsBackgroundLoaderForDownloadsEnabled();
 
+// Returns true if concurrent background loading is enabled for svelte.
+bool IsOfflinePagesSvelteConcurrentLoadingEnabled();
+
 // Returns true if downloading a page asynchonously is enabled.
 bool IsOfflinePagesAsyncDownloadEnabled();