Consider the following test: https://link-double-load.glitch.me/, which has a link rel=stylesheet. A script adds an onload event handler to the <link>, which is a function that indicates the number of times said handler is called. The script then sets the `href` attribute (to trigger a load) on the element twice. Chrome indicates the handler is called once, while Firefox indicates that the handler is called twice, which is the expected result.

I have not written WPTs for this, just have a POC in the form of the glitch page.

Seemingly related: https://crbug.com/674518