void RenderStyle::adjustBackgroundLayers()
{
    if (backgroundLayers()->next()) {
        // First we cull out layers that have no properties set.
        accessBackgroundLayers()->cullEmptyLayers();
        
        // Next we repeat patterns into layers that don't have some properties set.
        accessBackgroundLayers()->fillUnsetProperties();
    }
}
bool RenderStyle::hasEntirelyFixedBackground() const
{
    return allLayersAreFixed(backgroundLayers());
}