Remove value packing and custom style building for text-underline-position.

Source/core/css/CSSProperties.in

 // FIXME: When we have all the properties using the new StyleBuilder, we
 //   should use this for make_css_property_names.py
 // Note that type_name is currently only used for non-custom value application
 // and when explicitly referred to in generated applicators.
 // Note: Mandatory blank line to skip parameter parsing phase
 
 align-content
 align-items custom_all
 align-self custom_all
 background-attachment custom_all
@@ skipping 240 matching lines @@
 -webkit-tap-highlight-color converter=convertColor
 -webkit-text-combine type_name=TextCombine
 -webkit-text-emphasis-color custom_all
 -webkit-text-emphasis-position type_name=TextEmphasisPosition
 -webkit-text-emphasis-style custom_all
 -webkit-text-fill-color custom_all
 -webkit-text-orientation custom_value
 -webkit-text-security
 -webkit-text-stroke-color custom_all
 -webkit-text-stroke-width converter=convertTextStrokeWidth
-text-underline-position custom_value
+text-underline-position type_name=TextUnderlinePosition
 transform custom_value
 -webkit-transform use_handlers_for=CSSPropertyTransform
 transform-origin custom_all
 -webkit-transform-origin-x converter=convertLength
 -webkit-transform-origin-y converter=convertLength
 -webkit-transform-origin-z converter=convertComputedLength<float>
 transform-style name_for_methods=TransformStyle3D
 -webkit-transform-style name_for_methods=TransformStyle3D
 -webkit-transition-delay custom_all
 -webkit-transition-duration custom_all
@@ skipping 89 matching lines @@
 unicode-range skip
 -webkit-font-size-delta skip
 -webkit-text-decorations-in-effect skip
 max-zoom skip
 min-zoom skip
 user-zoom skip
 orientation skip
 enable-background skip
 invalid skip
 all skip