[Enhancement] Support nodes within other frames

[Craga89]

Added a getOwnerDocument utility that resolves the correct document based on the DraggableCores associated DOMElement. This enables usage of react-draggable on nodes that are rendered within an <iframe />.

[STRML]

Hey, nicely done!

Could you add a quick test case for it?

[Craga89]

Hmmm, I'm not too up-to-date with the TestUtils! Currently using react-frame-component to render into an Iframe, so we'd probably need to do that, but since it uses the unstable_renderSubtreeIntoContainer ReactDOM utility not sure if it would work within the tests?

[Craga89]

Actually, maybe I just need to test that getOwnerDocument works as expected? That should be easy enough.

[STRML]

Yeah - rendering iframed components is a little crazy IMO and breaks all sorts of assumptions. To test it properly I don't mind installing react-frame-component as a devDep.

[Craga89]

👍 I'll give it a shot when I get some time

[STRML]

Closing this in favor of #177 which also handles window.getComputedStyle(), which has problems with iframes.

[STRML]

Thanks anyhow for the contribution and I apologize that it got left here for this long.