higher timeout value for iframe responses handlers

lib/single-file/frame-tree.js

@@ -27,7 +27,7 @@ this.frameTree = this.frameTree || (() => {
 	const INIT_REQUEST_MESSAGE = "initRequest";
 	const INIT_RESPONSE_MESSAGE = "initResponse";
 	const TARGET_ORIGIN = "*";
-	const TIMEOUT_INIT_REQUEST_MESSAGE = 500;
+	const TIMEOUT_INIT_REQUEST_MESSAGE = 750;
 	const PREFIX_VALID_FRAME_URL = /^https?:\/\//;
 	const TOP_WINDOW_ID = "0";
 	const WINDOW_ID_SEPARATOR = ".";