diff --git a/common/security-features/resources/common.sub.js b/common/security-features/resources/common.sub.js
index b43417b417c189..cdd20a9d8daece 100644
--- a/common/security-features/resources/common.sub.js
+++ b/common/security-features/resources/common.sub.js
@@ -286,9 +286,17 @@ function bindEvents2(resolveObject, resolveEventName, rejectObject, rejectEventN
 function createElement(tagName, attrs, parentNode, doBindEvents) {
   var element = document.createElement(tagName);
 
-  if (doBindEvents)
+  if (doBindEvents) {
     bindEvents(element);
-
+    if (element.tagName == "IFRAME" && !('srcdoc' in attrs || 'src' in attrs)) {
+      // If we're loading a frame, ensure we spin the event loop after load to
+      // paper over the different event timing in Gecko vs Blink/WebKit
+      // see https://github.com/whatwg/html/issues/4965
+      element.eventPromise = element.eventPromise.then(() => {
+        return new Promise(resolve => setTimeout(resolve, 0))
+      });
+    }
+  }
   // We set the attributes after binding to events to catch any
   // event-triggering attribute changes. E.g. form submission.
   //
diff --git a/lint.whitelist b/lint.whitelist
index be6ae4f0314942..48d7e9d6a747b9 100644
--- a/lint.whitelist
+++ b/lint.whitelist
@@ -282,6 +282,7 @@ GENERATE_TESTS: shadow-dom/untriaged/shadow-trees/upper-boundary-encapsulation/w
 GENERATE_TESTS: shadow-dom/untriaged/shadow-trees/upper-boundary-encapsulation/window-named-properties-003.html
 
 # Intentional use of setTimeout
+SET TIMEOUT: common/security-features/resources/common.sub.js
 SET TIMEOUT: css/css-fonts/font-display/font-display.html
 SET TIMEOUT: css/css-fonts/font-display/font-display-change.html
 SET TIMEOUT: css/css-fonts/font-display/font-display-change-ref.html