iframe resizing with scrollheight in chrome/safari

Before you ask for the height of the document inside the iframe you should set the height of the iframe object to "auto". Something like this:

objIframe = document.getElementById('theIframeId');    
objIframe.style.height = 'auto';

And now:

document.body.scrollHeight

returns the actual height of the document.

Did you try using document.documentElement.scrollHeight instead?