Description

Our boolean attribute handling tries to keep boolean attribute values valid according to the spec, by always setting the lowercased attribute name regardless of what value was set. However, we do this for all elements whether the boolean attribute is valid on that element or not. This is especially troublesome for custom elements.

Rather than checking the nodeName of the element to ensure the boolean attribute applies to that element, it may be doable to just allow any string through. It may not be technically valid, but I think it works in all browsers to set any string. We'd still want to keep the special handling for the value false (i.e. remove the attribute rather than set "false", which is actually true). Note that the string "false" would still be passed through.

Link to test case

See angular/angular.js#16602 (comment) for background.