Demote 'line-height' to a low priority property.

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 79 matching lines @@
 font-variant inherited, font, type_name=FontVariant, name_for_methods=Variant
 font-variant-ligatures inherited, font, name_for_methods=VariantLigatures, converter=convertFontVariantLigatures
 font-weight animatable, inherited, font, type_name=FontWeight, name_for_methods=Weight, converter=convertFontWeight
 -webkit-font-feature-settings inherited, font, name_for_methods=FeatureSettings, converter=convertFontFeatureSettings
 -webkit-font-smoothing inherited, font, type_name=FontSmoothingMode
 -webkit-locale inherited, custom_value
 -webkit-text-orientation inherited, custom_value
 -webkit-writing-mode inherited, custom_value
 text-rendering inherited, font, type_name=TextRenderingMode
 zoom animatable, custom_all
-line-height animatable, inherited, getter=specifiedLineHeight, custom_value
 
 align-content
 align-items custom_all
 alignment-baseline svg
 align-self custom_all
 backface-visibility
 background-attachment custom_all
 background-blend-mode custom_all
 background-clip custom_all
 background-color animatable, custom_all
@@ skipping 73 matching lines @@
 grid-template-rows runtime_flag=CSSGridLayout, custom_all
 height animatable, initial=initialSize, converter=convertLengthSizing
 image-rendering inherited
 isolation runtime_flag=CSSCompositing
 justify-content
 justify-items runtime_flag=CSSGridLayout, custom_all
 justify-self runtime_flag=CSSGridLayout, custom_all
 left animatable, initial=initialOffset, converter=convertLengthOrAuto
 letter-spacing animatable, inherited, initial=initialLetterWordSpacing, converter=convertSpacing
 lighting-color animatable, svg, converter=convertSVGColor
+line-height animatable, inherited, getter=specifiedLineHeight, custom_value
 list-style-image animatable, inherited, custom_value
 list-style-position inherited
 list-style-type inherited
 margin-bottom animatable, initial=initialMargin, converter=convertLengthOrAuto
 margin-left animatable, initial=initialMargin, converter=convertLengthOrAuto
 margin-right animatable, initial=initialMargin, converter=convertLengthOrAuto
 margin-top animatable, initial=initialMargin, converter=convertLengthOrAuto
 marker-end inherited, svg, name_for_methods=MarkerEndResource, converter=convertFragmentIdentifier
 marker-mid inherited, svg, name_for_methods=MarkerMidResource, converter=convertFragmentIdentifier
 marker-start inherited, svg, name_for_methods=MarkerStartResource, converter=convertFragmentIdentifier
@@ skipping 311 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