var contents = Transferable.of(...);
var containerLocation = "/path/to/file";
withCopyFileToContainer(contents, containerLocation)

Relevant spec sections:

https://drafts.csswg.org/selectors-4/#the-dir-pseudo
https://html.spec.whatwg.org/multipage/semantics-other.html#selector-ltr

The interesting cases to test are from the definition of "directionality" in HTML:
https://html.spec.whatwg.org/multipage/dom.html#the-directionality

• element with dir="ltr" matches :dir(ltr)
• root element without dir attr

Can we have configurable timeout to fail request fast?