Add a generated ComputedStyleBase class that ComputedStyle extends

third_party/WebKit/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 should be virtually identical to the
 // properties they alias. Minor parsing differences are allowed as long as
 // the CSSValues created are of the same format of the aliased property.
 
 
 // - runtime_flag=CSSGridLayout
 // The flag on RuntimeEnabledFeatures conditionally enables the property.
 // This doesn't currently work with alias_for.
 
 
 // - descriptor_only
 // These are actually descriptors and not CSS properties. Properties with
 // the same name as a descriptor do not get this flag.
 
 
 // - longhands=property;other-property
 // The property is a shorthand for several other properties.
 
+// keyword_only
+// These properties only store keyword values. This is used when
+// generating the ComputedStyle storage for the property. The initial
+// value for this property on a ComputedStyle is the first keyword in
+// the specified list of keywords.
+// TODO(sashab, meade): Remove this once TypedOM types are specified for
+// every property, since this value can be inferred from that.
+
+// - keywords=[keyword1|keyword2]
+// This specifies all valid keyword values for the property.
+// TODO(sashab): Once all properties are represented here, delete
+// CSSValueKeywords.in and use this list instead.
 
 // Flags which go into CSSOMTypes:
 // - typedom_types=[Type|OtherType]
 // The property can take types specified in typedom_types for CSS Typed OM.
 // Keyword does not need to be specified as every property can take keywords.
-// - keywords=[keyword1|keyword2]
-// The property can take these keywords.
 // - supports_multiple
 // The property supports a list of values.
 // - supports_percentage
 // The property supports percentage types.
 
 
 // Flags which go into CSSPropertyMetadata:
 // - interpolable
 // The interpolable flag indicates whether a property can be animated smoothly.
 // If this flag is set, the property should also be added to the switch
@@ skipping 287 matching lines @@
 translate runtime_flag=CSSIndependentTransformProperties, converter=convertTranslate, interpolable
 rotate runtime_flag=CSSIndependentTransformProperties, converter=convertRotate, interpolable
 scale runtime_flag=CSSIndependentTransformProperties, converter=convertScale, interpolable
 transition-delay custom_all
 transition-duration custom_all
 transition-property custom_all
 transition-timing-function custom_all
 unicode-bidi
 vector-effect svg
 vertical-align interpolable, custom_inherit, custom_value
-visibility interpolable, inherited
+visibility interpolable, inherited, keyword_only, keywords=[visible|hidden|collapse]
 x interpolable, svg, converter=convertLength
 y interpolable, svg, converter=convertLength
 -webkit-appearance type_name=ControlPart
 -webkit-app-region custom_all
 -webkit-background-clip use_handlers_for=CSSPropertyBackgroundClip
 -webkit-background-origin use_handlers_for=CSSPropertyBackgroundOrigin
 -webkit-border-horizontal-spacing interpolable, inherited, name_for_methods=HorizontalBorderSpacing, converter=convertComputedLength<short>
 -webkit-border-image initial=initialNinePieceImage, custom_value
 -webkit-border-vertical-spacing interpolable, inherited, name_for_methods=VerticalBorderSpacing, converter=convertComputedLength<short>
 -webkit-box-align type_name=EBoxAlignment
@@ skipping 230 matching lines @@
 -webkit-shape-outside alias_for=shape-outside
 -webkit-text-size-adjust alias_for=text-size-adjust
 -webkit-transform alias_for=transform
 -webkit-transform-origin alias_for=transform-origin
 -webkit-transform-style alias_for=transform-style
 -webkit-transition alias_for=transition
 -webkit-transition-delay alias_for=transition-delay
 -webkit-transition-duration alias_for=transition-duration
 -webkit-transition-property alias_for=transition-property
 -webkit-transition-timing-function alias_for=transition-timing-function