Hum, it seems like problem here is that ScrollView::scroll calls ScrollView::platformScroll() for Mac, that this method is just stubbed out.
It would be helpful to know how scrolling working on Mac, when for example user taps DOWN_ARROW key.
@Dave or simon, could you please point me to the code?
It might happen through the native NSScrollView machinery, I'm not sure.
After applying the patches from https://bugs.webkit.org/show_bug.cgi?id=49382, this test is passing on mac.
Created attachment 74967 [details]
Remove test from skip list.
Committed r72791: <http://trac.webkit.org/changeset/72791>