When cnn.com does layout, there are a lot of calls to RenderBox::computeRectForRepaint(), via RenderLayer::updateLayerPositions(). It's inefficient for the following reasons: 1. We don't track whether any layers actually changed, so we may not actually have to do any work 2. We're walking down the RenderLayer tree, but for each layer walking back up the renderers doing computeRectForRepaint(), so it's > O(N)
<rdar://problem/9216902>
Ideas here: 1. remove the repaint code from layers (hyatt says it's old) 2. have layout detect when a layer is moved or resized