1868 iframe design research

@mlippert, @seannives 
As part of the iframe story, I created a testpage for multiple divs (testpage-divs.xhtml).

I'd like to merge this to the master, so I can use this test page to show brix and ask questions. 

Please code review and let me know if you are ok merging this to master.

This pull request contains no modification other than files in test/integration. 

The most important change is the addition of the
tests/integration/testpage-divs.xhtml