Move style building for grid-auto-flow to StyleBuilderConverter.

Source/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
 
 
 // - alias_for=other-property
 // Properties specifying alias_for do not get their own enum and instead map
 // directly onto the CSSPropertyID they alias. Currently this means that the
 // UseCounter will not pick up on these (crbug.com/304855)
 
@@ skipping 158 matching lines @@
 flex-direction
 flex-grow animatable, type_name=float
 flex-shrink animatable, type_name=float
 flex-wrap
 float type_name=EFloat, name_for_methods=Floating
 flood-color animatable, svg, converter=convertSVGColor
 flood-opacity animatable, svg, converter=convertNumberOrPercentage
 glyph-orientation-horizontal inherited, svg, converter=convertGlyphOrientation
 glyph-orientation-vertical inherited, svg, custom_value
 grid-auto-columns runtime_flag=CSSGridLayout, converter=convertGridTrackSize
-grid-auto-flow runtime_flag=CSSGridLayout, custom_value
+grid-auto-flow runtime_flag=CSSGridLayout, converter=convertGridAutoFlow
 grid-auto-rows runtime_flag=CSSGridLayout, converter=convertGridTrackSize
 grid-column-end runtime_flag=CSSGridLayout, converter=convertGridPosition
 grid-column-start runtime_flag=CSSGridLayout, converter=convertGridPosition
 grid-row-end runtime_flag=CSSGridLayout, converter=convertGridPosition
 grid-row-start runtime_flag=CSSGridLayout, converter=convertGridPosition
 grid-template-areas runtime_flag=CSSGridLayout, custom_all
 grid-template-columns runtime_flag=CSSGridLayout, custom_all
 grid-template-rows runtime_flag=CSSGridLayout, custom_all
 height animatable, initial=initialSize, converter=convertLengthSizing
 image-rendering inherited
@@ skipping 337 matching lines @@
 -webkit-flex-flow alias_for=flex-flow
 -webkit-flex-grow alias_for=flex-grow
 -webkit-flex-shrink alias_for=flex-shrink
 -webkit-flex-wrap alias_for=flex-wrap
 -webkit-justify-content alias_for=justify-content
 -webkit-opacity alias_for=opacity
 -webkit-order alias_for=order
 -webkit-shape-image-threshold alias_for=shape-image-threshold
 -webkit-shape-margin alias_for=shape-margin
 -webkit-shape-outside alias_for=shape-outside