WKWebView/WKView's setMagnification: and setMagnification:centeredAtPoint: both expose the somewhat bizarre but widespread notion of a scale "origin", which really just translates into the scroll position post-scale. We intended for setMagnification: and setMagnification:centeredAtPoint: to use view-relative points (and points within the view instead of (negative) scroll position) to center the zoom, as those make much more sense as exposed API. <rdar://problem/15965239>
Created attachment 229276 [details] patch
http://trac.webkit.org/changeset/167253