I understand that `displayRenderedIcon` has a race condition (we revoke the object url in the onload handler, so maybe, sometimes, we're revoking before calling onDragLeave (or onDragLeave is doing some asynchronous stuff, I don't know). 

So I have 2 questions here:
* I'd really like to know which code is triggering the object URL revalidation. The fact that it does not happen on v1.0.1 could make it easy to find it.
* Couldn't we make `displayRenderedIcon` take a callback instead of creating a new method ?