I think the suggested solution of 'ignore <link> tags that have a "mask" attribute' also creates needless work, and is backward-incompatible --- existing browsers are looking for "rel=icon" for a favicon, and will ignore "mask" or other unknown attributes.
Exactly. New tags should "fail safe" in old browsers (i.e. do "nothing"). The problem with the mask attribute and "only render the last one" concept is that older browsers might not be doing so already, and therefore the new tag doesn't fail safe (it is fail-active, so older browsers might render solid black favicons).
Seems silly. They should just use a new rel value for this specific purpose. Although broadly speaking it feels like the icon rel has had its day, and now we need a replacement that is DESIGNED to support multiple resolutions, and things like masks.
« If multiple icons are provided, the user agent must select the most appropriate icon according to the type, media, and sizes attributes. If there are multiple equally appropriate icons, user agents must use the last one declared in tree order at the time that the user agent collected the list of icons. »
