This is easily reproduced on pages like reddit.com, browsing through the comments, zooming the page and trying to select a word. <rdar://problem/17138059>
Created attachment 233734 [details] Patch
Comment on attachment 233734 [details] Patch The change makes sense. I would create a second rect (a FloatRect) especially for that purpose. Something like: FloatRect boundingRectInScrollViewCoordinates(boundingRect); boundingRectInScrollViewCoordinates.scale(...). To make it explicit which that rect is not in document coordinates.
Committed revision 170388.