How to scale canvas & contents to parent div, not viewport

I need an Adobe Animate canvas to scale to fill a parent div instead of the browser window?

I don't need functionality any more complicated than Animate's existing scale options, I simply need them to respect the parent div's dimensions instead of the viewport's.

I tried hacking the html & js that Animate creates, but I'm not savvy enough to stumble my way through it. Someone, please tell me this is possible in a relatively straightforward manner.