iframes seem to occasionally doubly scale or scale incorrectly when pageScaleFactor...

iframes seem to occasionally doubly scale or scale incorrectly when pageScaleFactor != 1.0
https://bugs.webkit.org/show_bug.cgi?id=70552

Reviewed by Simon Fraser.

Source/WebCore:

Test: fast/frames/iframe-double-scale-contents.html

The iframe's document style was using the page's scale factor, rather than the frame's (1.0).
If the page scale factor was set after layout was complete, then this would have no impact because the iframe's document style and layout is not recomputed,
but if the page scale factor is set prior to creating and laying out the iframe, the iframe's content would be doubly scaled.

* css/CSSStyleSelector.cpp:
(WebCore::CSSStyleSelector::styleForDocument):

LayoutTests:

* fast/frames/iframe-double-scale-contents-expected.png: Added.
* fast/frames/iframe-double-scale-contents-expected.txt: Added.
* fast/frames/iframe-double-scale-contents.html: Added.
* fast/frames/resources/iframe-content-scaling-bug-iframe.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@98637 268f45cc-cd09-0410-ab3c-d52691b4dbfc