register message handler on capture and stop the event

lib/single-file/frame-tree.js

@@ -49,8 +49,10 @@ this.frameTree = this.frameTree || (() => {
 				const port = event.ports[0];
 				port.onmessage = event => initResponse(event.data);
 			}
+			event.preventDefault();
+			event.stopPropagation();
 		}
-	}, false);
+	}, true);
 	return {
 		getAsync: async options => {
 			const sessionId = options.sessionId;