Remove backface visibility

sky/engine/core/css/CSSProperties.in

 // This file specifies all the CSS properties we support and the necessary
 // information for our code generation. The various supported arguments
 // are described below with example usage
 
 // We should remove all those marked OBSOLETE now
 // We should remove all those marked LAYOUT once we have custom layout
 // We should remove all those marked ANIMATIONS once we have an animation system
 
 // - alias_for=other-property
 // Properties specifying alias_for do not get their own enum and instead map
@@ skipping 93 matching lines @@
 
 // LAYOUT
 align-content
 
 // LAYOUT
 align-items custom_all
 
 // LAYOUT
 align-self custom_all
 
-backface-visibility
 background-attachment custom_all
 background-clip custom_all
 background-color animatable, custom_all
 background-image animatable, custom_all
 background-origin custom_all
 background-position-x animatable, custom_all
 background-position-y animatable, custom_all
 background-repeat-x custom_all
 background-repeat-y custom_all
 background-size animatable, custom_all
@@ skipping 179 matching lines @@
 animation-name custom_all
 
 // ANIMATION
 animation-play-state custom_all
 
 // ANIMATION
 animation-timing-function custom_all
 
 filter animatable, custom_value
 -webkit-aspect-ratio inherited, custom_all
--webkit-backface-visibility use_handlers_for=CSSPropertyBackfaceVisibility
 -webkit-background-clip use_handlers_for=CSSPropertyBackgroundClip
 -webkit-background-composite custom_all
 -webkit-background-origin use_handlers_for=CSSPropertyBackgroundOrigin
 -webkit-background-size animatable, use_handlers_for=CSSPropertyBackgroundSize
 
 // LAYOUT
 -webkit-border-horizontal-spacing animatable, inherited, name_for_methods=HorizontalBorderSpacing, converter=convertComputedLength<short>
 
 -webkit-border-image initial=initialNinePieceImage, custom_value
 
@@ skipping 164 matching lines @@
 -webkit-border-after longhands=-webkit-border-after-width;-webkit-border-after-style;-webkit-border-after-color
 -webkit-border-before longhands=-webkit-border-before-width;-webkit-border-before-style;-webkit-border-before-color
 -webkit-border-end longhands=-webkit-border-end-width;-webkit-border-end-style;-webkit-border-end-color
 // "-webkit-border-radius: 1px 2px" behaves as "border-radius: 1px / 2px"
 -webkit-border-radius longhands=border-top-left-radius;border-top-right-radius;border-bottom-right-radius;border-bottom-left-radius
 -webkit-border-start longhands=-webkit-border-start-width;-webkit-border-start-style;-webkit-border-start-color
 -webkit-text-emphasis longhands=-webkit-text-emphasis-style;-webkit-text-emphasis-color
 -webkit-text-stroke longhands=-webkit-text-stroke-width;-webkit-text-stroke-color
 -webkit-transform-origin longhands=-webkit-transform-origin-x;-webkit-transform-origin-y;-webkit-transform-origin-z
 transition longhands=transition-property;transition-duration;transition-timing-function;transition-delay