Add support for fallback content for the frame. This includes main and subframes.

content/browser/loader/url_loader_request_handler.cc

Index: content/browser/loader/url_loader_request_handler.cc
diff --git a/content/browser/loader/url_loader_request_handler.cc b/content/browser/loader/url_loader_request_handler.cc
index 0925e224cfb232ad8f86ce7bfd709a82bd323a50..b6fea3becd09821484324f279d59828ccb10980e 100644
--- a/content/browser/loader/url_loader_request_handler.cc
+++ b/content/browser/loader/url_loader_request_handler.cc
@@ -11,4 +11,19 @@ URLLoaderRequestHandler::MaybeCreateSubresourceFactory() {
   return nullptr;
 }
 
+bool URLLoaderRequestHandler::MaybeGetFallbackForResponse(
+    const ResourceResponseHead& response,
+    mojom::URLLoaderClientPtr* client,
+    mojom::URLLoaderRequest* request) {
+  return false;
+}
+
+bool URLLoaderRequestHandler::MaybeGetFallbackForRedirect(
+    const ResourceResponseHead& response,
+    const net::RedirectInfo& redirect_info,
+    mojom::URLLoaderClientPtr* client,
+    mojom::URLLoaderRequest* request) {
+  return false;
+}
+
 }  // namespace content