When an iframe does not handle a mouse wheel event it is currently dispatched to the parent iframe. Mouse wheel events are unique in this dispatching aspect and other vendors FireFox and Microsoft both don't dispatch the event to the parent iframe. This request is to make Chrome match FF and Edge. Some public discussion has happened on Fireכox's bug where a web developer asked Mozilla to implement similar behavior to chrome.
Docs: https://bugzilla.mozilla.org/show_bug.cgi?id=1084121
Samples: http://dtapuska.github.io/564042/iframe-scroll.html