Created attachment 236717 [details] Test case To reproduce the bug, open the test case in Safari. The content is pushed down such that there is a white gap at the top and only the top (end) of the content is visible.
Caused by http://trac.webkit.org/r168244, the fix for bug 132535.
<rdar://problem/18040990>
Fixed, probably in https://trac.webkit.org/changeset/194487.
Not fixed.
The bug is that RLC sets the correct position of the root content layer at: m_rootContentLayer->setPosition(FloatPoint(documentRect.x(), documentRect.y() + m_renderView.frameView().yPositionForRootContentLayer())); but the scrolling thread overwrite that with a bad position at: m_scrolledContentsLayer.get().position = FloatPoint(m_scrolledContentsLayer.get().position.x, FrameView::yPositionForRootContentLayer(position, topContentInset, headerHeight())); which ignores the documentRect part.
Created attachment 269547 [details] Patch
https://trac.webkit.org/changeset/195445