Add a fast-path for independent inherited properties

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.
 
@@ skipping 27 matching lines @@
 // 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
 // statements in AnimatedStyleBuilder, CSSPropertyEquality and
 // CSSAnimatableValueFactory.
 // - inherited
 // The property will inherit by default if no value is specified, typically
 // mentioned in specifications as "Inherited: yes"
 
+// - independent

[esprehn, 2016/07/19 03:46:26]

I think you want to mention that StyleAdjuster can't mess with properties that
take this fast path?

[sashab, 2016/07/19 06:32:38]

Thanks :) Added that, and cleaned up this comment too.

+// This property affects only one property on ComputedStyle, and can be
+// set directly during inheritance instead of forcing a recalc.
+// Recalcs only happen during a change propagation if at least one non-
+// independent property is changed.
+// Additionally, a change by an independent property must cause

[Timothy Loh, 2016/07/19 01:29:32]

Why?

[sashab, 2016/07/19 03:31:34]

Removed?

+// ComputedStyle to change (e.g. font-size: 10px; and font-size: 1em;

[esprehn, 2016/07/19 03:46:26]

I'm not sure this is a good example, font-size impacts all properties that use
relative units, which is why it's a "high priority property". We'd need to store
tons of information but the comment doesn't really explain it.

[sashab, 2016/07/19 06:32:38]

Removed this comment, its not really needed anyway.

+// result in the same ComputedStyle, but a change has still happened.
+// To make font-size independent, more information about the original
+// value needs to be stored).
 
 // The remaining arguments are used for the StyleBuilder and allow us to
 // succinctly describe how to apply properties. When default handlers are not
 // sufficient, we should prefer to use converter, and failing that define
 // custom property handlers in StyleBuilderCustom.cpp. We only should use
 // StyleBuilderFunctions.cpp.tmpl to define handlers when there are multiple
 // properties requiring the same handling, but converter doesn't suffice.
 
 // - font
 // The default property handlers call into the FontBuilder instead of setting
@@ skipping 206 matching lines @@
 overflow-wrap inherited
 overflow-x type_name=EOverflow
 overflow-y type_name=EOverflow
 padding-bottom interpolable, initial=initialPadding, converter=convertLength
 padding-left interpolable, initial=initialPadding, converter=convertLength
 padding-right interpolable, initial=initialPadding, converter=convertLength
 padding-top interpolable, initial=initialPadding, converter=convertLength
 paint-order inherited, svg, converter=convertPaintOrder
 perspective interpolable, converter=convertPerspective
 perspective-origin interpolable, converter=convertPosition
-pointer-events inherited
+pointer-events inherited, independent
 position custom_inherit
 quotes inherited, converter=convertQuotes
 resize custom_value
 right typedom_types=[Length], keywords=[auto], supports_percentage, interpolable, initial=initialOffset, converter=convertLengthOrAuto
 r interpolable, svg, converter=convertLength
 rx interpolable, svg, converter=convertLengthOrAuto
 ry interpolable, svg, converter=convertLengthOrAuto
 scroll-behavior runtime_flag=CSSOMSmoothScroll, type_name=ScrollBehavior
 scroll-snap-type runtime_flag=CSSScrollSnapPoints, type_name=ScrollSnapType
 scroll-snap-points-x runtime_flag=CSSScrollSnapPoints, converter=convertSnapPoints
@@ skipping 43 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, independent
 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