[resize-observer-1] Resize loop errors are not displayed

[just-boris]

In the Resize Observer there is a section about handing resize loops:

https://www.w3.org/TR/resize-observer/#deliver-resize-error

To deliver resize loop error notification run these steps:

1. Create a new ErrorEvent.
2. Initialize event’s message slot to "ResizeObserver loop completed with undelivered notifications.".
3. Report the exception event.

However, the step "Report the exception event" is ambiguous. Different browsers handle it differently:

Safari – prints the error message to the console
Chrome, Firefox – do not print anything to the console.

Demo: https://output.jsbin.com/vusorevisi

To be fair, all browsers report the error via window.onerror handler, but if it is missing, there is no way to see the error message.

What is the expected result here? Should browsers always print the message, like it happens with unhandled JavaScript errors, for example?

[hilts-vaughan]

Related: #5488