Created attachment 272381 [details] snapshot Reftest results are all mirrored vertically on iOS.
I have a fix.
Created attachment 274153 [details] Patch
http://trac.webkit.org/changeset/198242
Looks like this may have caused a few test failures on mac-wk2 <https://build.webkit.org/results/Apple%20El%20Capitan%20Release%20WK2%20(Tests)/r198243%20(4335)/results.html> Regressions: Unexpected image-only failures (3) printing/quirks-percentage-height-body.html [ ImageOnlyFailure ] printing/quirks-percentage-height.html [ ImageOnlyFailure ] printing/standards-percentage-heights.html [ ImageOnlyFailure ]
That's a bit concerning and bizarre. Will investigate!
I filed https://bugs.webkit.org/show_bug.cgi?id=155543