Basic image - no style - can be directly composited
In order to run this test you should enable the debugging options that indicate what type of compositing layer is being used.
defaults write com.apple.Safari WebCoreLayerRepaintCounter -bool yes defaults write com.apple.Safari WebCoreLayerBorders -bool yes
Directly composited image layers will have a yellow border and no repaint counter.
Basic image - no style - can be directly composited
5px blue border - can NOT be directly composited
margin - can NOT be directly composited
solid background - can be directly composited
background image - can NOT be directly composited
rotated but otherwise no style - can be directly composited