No initial resize of embeded activity when blocking third party cookies

I try to embed a drag-the-words h5p activity from my wordpress into anonther website with a different URL. When a browser blocks all third party cookies (I think this is the default in the new firefox and chrome browsers) there is no initial "resize" of the activity even if i place the resize.js on the other server. 

Chrome tells me "Uncaught DOMException: Failed to read the 'localStorage' property from 'Window': Access is denied for this document."

But when drag an element on the mouseup event the activity is resizing and everything looks perfect.

Does someone know a workaround here?