should setting open attribute cancel timeouts?

[fergald]

What should

toast.show();
toast.setAttribtue("open", "");

do? Should it still close after a timeout?

toast.show();
toast.removeAttribtue("open");
toast.setAttribtue("open", "");

will cancel the close-after-timeout callback.

Whatever the answer is, we should make it clear in the explainer how manipulating the attribute impacts the timeout behaviour.