FrameView->m_lastPaintTime is only updated from FrameView::paintContents, not RenderLayerBacking::paintContents. This causes m_lastPaintTime to never get updated in the tiled drawing case. This can cause horrible things, like the HTML parser incessantly yielding even after the page has always painted, on a page with lots of inline <script>s, etc.
Created attachment 141481 [details] patch
http://trac.webkit.org/changeset/116799
<rdar://problem/11248475>