Fixes bug 76 where fixed page background was incorrectly scaled. (take 2)

Modified to set the width and height of the iframe to the
original size rather than the viewed size.

This fixes the specific case in bug76 with a one page view that has a background image that gets scaled incorrectly. I tested with other files and this does not seem to adversely affect other rendering. I suspect that is because the outer div of the iframe as the desired width and height. I would be happy to test more with guidance from folks that may understand the implications of this change better than me.
I disagree, it must be the scaled dimensions, not the original meta width / height. Otherwise, the iframe crops content when scale > 1 (tested with books that have a "background" image that fills the entire viewport precisely).