Extension throws cross origin error during startup for some iframes.

[joshduck]

When checking parent windows for the x-wtf-options element (via topWindow.document.querySelector('x-wtf-options');) the browser will throw if the lookup is disallowed by cross origin constraints.

This exception is caught, but if I have Chrome set to break on uncaught exceptions then this creates a lot of friction on every single page load. The only way solution is to disable pausing or disabling the WTF extension.

It doesn't seem like there is a way to probe the outer frame for cross origin lookups, but postMessage should achieve the same results and is relatively lightweight to implement.