// If this layer was previously squashed, we need to remove its reference to a groupedMapping right away, so
// that computing repaint rects will know the layer's correct compositingState.
// FIXME: do we need to also remove the layer from it's location in the squashing list of its groupedMapping?
// If this layer was previously squashed, we need to remove its reference to a groupedMapping right away, so
// that computing repaint rects will know the layer's correct compositingState.
// FIXME: do we need to also remove the layer from it's location in the squashing list of its groupedMapping?