[css-transitions] add parsing support for the transition-behavior p…

…roperty

https://bugs.webkit.org/show_bug.cgi?id=266071
rdar://119378989

Reviewed by Tim Nguyen.

We add parsing support for the new `transition-behavior` property which we represent as a simple
boolean on the backing Animation object created for each group of `transition-` properties.

We make adjustments in this patch to always serialize the previously-existing `transition-`
properties for the `transition` shorthand to pass the tests in the existing WPT tests. The
new `transition-behavior` property is handled differently where it only gets serialized if
it cannot be omitted.

An issue was filed to see if the relevant tests are indeed correct: web-platform-tests/wpt#43574.

* LayoutTests/fast/css/shorthand-mismatched-list-crash-expected.txt:
* LayoutTests/fast/css/shorthand-mismatched-list-crash.html:
* LayoutTests/fast/css/transform-inline-style-expected.txt:
* LayoutTests/fast/css/transform-inline-style-remove-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/all-prop-revert-layer-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/css/css-transitions/parsing/transition-behavior-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/css/css-transitions/parsing/transition-shorthand-expected.txt:
* LayoutTests/platform/gtk/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* LayoutTests/platform/ios-wk2/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* LayoutTests/platform/ipad/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* LayoutTests/platform/mac-wk1/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* LayoutTests/platform/mac-wk1/imported/w3c/web-platform-tests/css/css-cascade/all-prop-revert-layer-expected.txt:
* LayoutTests/platform/wpe/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt:
* Source/WebCore/animation/CSSPropertyAnimation.cpp:
(WebCore::CSSPropertyAnimationWrapperMap::CSSPropertyAnimationWrapperMap):
* Source/WebCore/css/CSSProperties.json:
* Source/WebCore/css/CSSToStyleMap.cpp:
(WebCore::CSSToStyleMap::mapAnimationAllowsDiscreteTransitions):
* Source/WebCore/css/CSSToStyleMap.h:
* Source/WebCore/css/CSSValueKeywords.in:
* Source/WebCore/css/ComputedStyleExtractor.cpp:
(WebCore::valueForTransitionBehavior):
(WebCore::addValueForAnimationPropertyToList):
(WebCore::valueListForAnimationOrTransitionProperty):
(WebCore::animationShorthandValue):
(WebCore::ComputedStyleExtractor::valueForPropertyInStyle const):
(WebCore::ComputedStyleExtractor::addValueForAnimationPropertyToList): Deleted.
* Source/WebCore/css/ComputedStyleExtractor.h:
* Source/WebCore/css/ShorthandSerializer.cpp:
(WebCore::ShorthandSerializer::serializeLayered const):
* Source/WebCore/css/StylePropertyShorthand.cpp:
(WebCore::transitionShorthandForParsing):
* Source/WebCore/css/parser/CSSPropertyParser.cpp:
(WebCore::initialValueForLonghand):
(WebCore::consumeAnimationValueForShorthand):
* Source/WebCore/platform/animation/Animation.cpp:
(WebCore::Animation::Animation):
(WebCore::Animation::animationsMatch const):
* Source/WebCore/platform/animation/Animation.h:
(WebCore::Animation::isAllowsDiscreteTransitionsSet const):
(WebCore::Animation::isEmpty const):
(WebCore::Animation::clearAllowsDiscreteTransitions):
(WebCore::Animation::clearAll):
(WebCore::Animation::fillAllowsDiscreteTransitions):
(WebCore::Animation::isAllowsDiscreteTransitionsFilled const):
(WebCore::Animation::setAllowsDiscreteTransitions):
(WebCore::Animation::allowsDiscreteTransitions const):
(WebCore::Animation::initialAllowsDiscreteTransitions):
* Source/WebCore/platform/animation/AnimationList.cpp:
(WebCore::AnimationList::fillUnsetProperties):
* Source/WebCore/style/PropertyAllowlist.cpp:
(WebCore::Style::isValidMarkerStyleProperty):

Canonical link: https://commits.webkit.org/271759@main

LayoutTests/fast/css/shorthand-mismatched-list-crash-expected.txt

@@ -1,7 +1,7 @@
 Test for WebKit bug 31559: Crash with mismatched lists and shorthands.
 
-PASS para.style.webkitTransition is "width 1s, left 1s, 1s"
-PASS para.style.webkitTransition is "width 1s, left 1s, top"
+PASS para.style.webkitTransition is "width 1s ease 0s, left 1s ease 0s, all 1s ease 0s"
+PASS para.style.webkitTransition is "width 1s ease 0s, left 1s ease 0s, top 0s ease 0s"
 PASS successfullyParsed is true
 
 TEST COMPLETE

LayoutTests/fast/css/shorthand-mismatched-list-crash.html

@@ -17,14 +17,14 @@
   para.style.webkitTransition = 'width 1s, left 1s, top 1s';
   para.style.webkitTransitionProperty = 'width, left';
 
-  shouldBeEqualToString("para.style.webkitTransition", "width 1s, left 1s, 1s");
+  shouldBeEqualToString("para.style.webkitTransition", "width 1s ease 0s, left 1s ease 0s, all 1s ease 0s");
 
   // Test shorter shorthand
   para.style.webkitTransition = 'width 1s, left 1s';
   para.style.webkitTransitionProperty = 'width, left, top';
 
   // the next line will crash
-  shouldBeEqualToString("para.style.webkitTransition", "width 1s, left 1s, top");
+  shouldBeEqualToString("para.style.webkitTransition", "width 1s ease 0s, left 1s ease 0s, top 0s ease 0s");
 </script>
 <script src="../../resources/js-test-post.js"></script>
 </body>

LayoutTests/fast/css/transform-inline-style-expected.txt

@@ -1,6 +1,6 @@
 Tests reading inline style of transition, and -webkit-transform-origin
 https://bugs.webkit.org/show_bug.cgi?id=22594
 
-style: 1s, left 3s cubic-bezier(0.2, 0.3, 0.6, 0.8) 2s
+style: all 1s ease 0s, left 3s cubic-bezier(0.2, 0.3, 0.6, 0.8) 2s
 style: left 30%
 

LayoutTests/fast/css/transform-inline-style-remove-expected.txt

@@ -3,7 +3,7 @@ https://bugs.webkit.org/show_bug.cgi?id=22605
 
 All "after" results should be null/empty
 
-transition (before): 1s, left 3s cubic-bezier(0.2, 0.3, 0.6, 0.8) 2s
+transition (before): all 1s ease 0s, left 3s cubic-bezier(0.2, 0.3, 0.6, 0.8) 2s
 transition property (before): all, left
 transition duration (before): 1s, 3s
 transition timing function (before): ease, cubic-bezier(0.2, 0.3, 0.6, 0.8)

LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -346,6 +346,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/all-prop-revert-layer-expected.txt

@@ -331,6 +331,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/imported/w3c/web-platform-tests/css/css-transitions/parsing/transition-behavior-expected.txt

@@ -1,30 +1,30 @@
 
-FAIL e.style['transition-behavior'] = "normal" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition-behavior value 'normal' assert_true: transition-behavior doesn't seem to be supported in the computed style expected true got false
-FAIL e.style['transition-behavior'] = "allow-discrete" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition-behavior value 'allow-discrete' assert_true: transition-behavior doesn't seem to be supported in the computed style expected true got false
-FAIL e.style['transition'] = "allow-discrete display" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display' assert_true: 'allow-discrete display' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "allow-discrete display 3s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display 3s' assert_true: 'allow-discrete display 3s' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "allow-discrete display 3s 1s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display 3s 1s' assert_true: 'allow-discrete display 3s 1s' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "allow-discrete display 3s ease-in-out" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display 3s ease-in-out' assert_true: 'allow-discrete display 3s ease-in-out' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "allow-discrete display 3s ease-in-out 1s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display 3s ease-in-out 1s' assert_true: 'allow-discrete display 3s ease-in-out 1s' is a supported value for transition. expected true got false
+PASS e.style['transition-behavior'] = "normal" should set the property value
+PASS Property transition-behavior value 'normal'
+PASS e.style['transition-behavior'] = "allow-discrete" should set the property value
+PASS Property transition-behavior value 'allow-discrete'
+PASS e.style['transition'] = "allow-discrete display" should set the property value
+PASS Property transition value 'allow-discrete display'
+PASS e.style['transition'] = "allow-discrete display 3s" should set the property value
+PASS Property transition value 'allow-discrete display 3s'
+PASS e.style['transition'] = "allow-discrete display 3s 1s" should set the property value
+PASS Property transition value 'allow-discrete display 3s 1s'
+PASS e.style['transition'] = "allow-discrete display 3s ease-in-out" should set the property value
+PASS Property transition value 'allow-discrete display 3s ease-in-out'
+PASS e.style['transition'] = "allow-discrete display 3s ease-in-out 1s" should set the property value
+PASS Property transition value 'allow-discrete display 3s ease-in-out 1s'
 PASS e.style['transition'] = "asdf display" should not set the property value
 PASS e.style['transition'] = "display asdf" should not set the property value
-FAIL e.style['transition'] = "display allow-discrete 3s ease-in-out 1s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL e.style['transition'] = "display 3s allow-discrete ease-in-out 1s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL e.style['transition'] = "display 3s ease-in-out allow-discrete 1s" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL e.style['transition'] = "display 3s ease-in-out 1s allow-discrete" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'display allow-discrete 3s ease-in-out 1s' assert_true: 'display allow-discrete 3s ease-in-out 1s' is a supported value for transition. expected true got false
-FAIL Property transition value 'display 3s allow-discrete ease-in-out 1s' assert_true: 'display 3s allow-discrete ease-in-out 1s' is a supported value for transition. expected true got false
-FAIL Property transition value 'display 3s ease-in-out allow-discrete 1s' assert_true: 'display 3s ease-in-out allow-discrete 1s' is a supported value for transition. expected true got false
-FAIL Property transition value 'display 3s ease-in-out 1s allow-discrete' assert_true: 'display 3s ease-in-out 1s allow-discrete' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "allow-discrete display, normal opacity, color" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'allow-discrete display, normal opacity, color' assert_true: 'allow-discrete display, normal opacity, color' is a supported value for transition. expected true got false
-FAIL e.style['transition'] = "normal opacity, color, allow-discrete display" should set the property value assert_not_equals: property should be set got disallowed value ""
-FAIL Property transition value 'normal opacity, color, allow-discrete display' assert_true: 'normal opacity, color, allow-discrete display' is a supported value for transition. expected true got false
+PASS e.style['transition'] = "display allow-discrete 3s ease-in-out 1s" should set the property value
+PASS e.style['transition'] = "display 3s allow-discrete ease-in-out 1s" should set the property value
+PASS e.style['transition'] = "display 3s ease-in-out allow-discrete 1s" should set the property value
+PASS e.style['transition'] = "display 3s ease-in-out 1s allow-discrete" should set the property value
+PASS Property transition value 'display allow-discrete 3s ease-in-out 1s'
+PASS Property transition value 'display 3s allow-discrete ease-in-out 1s'
+PASS Property transition value 'display 3s ease-in-out allow-discrete 1s'
+PASS Property transition value 'display 3s ease-in-out 1s allow-discrete'
+PASS e.style['transition'] = "allow-discrete display, normal opacity, color" should set the property value
+PASS Property transition value 'allow-discrete display, normal opacity, color'
+PASS e.style['transition'] = "normal opacity, color, allow-discrete display" should set the property value
+PASS Property transition value 'normal opacity, color, allow-discrete display'
 

LayoutTests/imported/w3c/web-platform-tests/css/css-transitions/parsing/transition-shorthand-expected.txt

@@ -1,17 +1,17 @@
 
-FAIL e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-behavior assert_equals: transition-behavior should be canonical expected (string) "normal" but got (undefined) undefined
+PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-behavior
 PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-delay
 PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-duration
 PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-property
 PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should set transition-timing-function
 PASS e.style['transition'] = "1s -3s cubic-bezier(0, -2, 1, 3) top" should not set unrelated longhands
-FAIL e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-behavior assert_equals: transition-behavior should be canonical expected (string) "normal, normal" but got (undefined) undefined
+PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-behavior
 PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-delay
 PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-duration
 PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-property
 PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should set transition-timing-function
 PASS e.style['transition'] = "1s -3s, cubic-bezier(0, -2, 1, 3) top" should not set unrelated longhands
-FAIL e.style['transition'] = "cubic-bezier(0, -2, 1, 3) top, 1s -3s" should set transition-behavior assert_equals: transition-behavior should be canonical expected (string) "normal, normal" but got (undefined) undefined
+PASS e.style['transition'] = "cubic-bezier(0, -2, 1, 3) top, 1s -3s" should set transition-behavior
 PASS e.style['transition'] = "cubic-bezier(0, -2, 1, 3) top, 1s -3s" should set transition-delay
 PASS e.style['transition'] = "cubic-bezier(0, -2, 1, 3) top, 1s -3s" should set transition-duration
 PASS e.style['transition'] = "cubic-bezier(0, -2, 1, 3) top, 1s -3s" should set transition-property

LayoutTests/platform/gtk/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -346,6 +346,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/platform/ios-wk2/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -346,6 +346,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/platform/ipad/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -345,6 +345,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/platform/mac-wk1/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -345,6 +345,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/platform/mac-wk1/imported/w3c/web-platform-tests/css/css-cascade/all-prop-revert-layer-expected.txt

@@ -330,6 +330,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

LayoutTests/platform/wpe/imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml-expected.txt

@@ -346,6 +346,7 @@ PASS transform
 PASS transform-box
 PASS transform-origin
 PASS transform-style
+PASS transition-behavior
 PASS transition-delay
 PASS transition-duration
 PASS transition-property

Source/WebCore/animation/CSSPropertyAnimation.cpp

@@ -4138,6 +4138,7 @@ CSSPropertyAnimationWrapperMap::CSSPropertyAnimationWrapperMap()
         case CSSPropertyTextDecorationSkip:
         case CSSPropertyTextUnderlinePosition:
         case CSSPropertyTransition:
+        case CSSPropertyTransitionBehavior:
         case CSSPropertyTransitionDelay:
         case CSSPropertyTransitionDuration:
         case CSSPropertyTransitionProperty:

Source/WebCore/css/CSSProperties.json

@@ -6012,14 +6012,31 @@
                     "transition-property",
                     "transition-duration",
                     "transition-timing-function",
-                    "transition-delay"
+                    "transition-delay",
+                    "transition-behavior"
                 ]
             },
             "specification": {
                 "category": "css-transitions",
                 "url": "https://www.w3.org/TR/css3-transitions/#transition-shorthand-property"
             }
         },
+        "transition-behavior": {
+            "values": [
+                "normal",
+                "allow-discrete"
+            ],
+            "animatable": true,
+            "codegen-properties": {
+                "name-for-methods": "AllowsDiscreteTransitions",
+                "separator": ",",
+                "parser-grammar": "<transition-behavior-value>#"
+            },
+            "specification": {
+                "category": "css-transitions",
+                "url": "https://drafts.csswg.org/css-transitions-2/#transition-behavior-property"
+            }
+        },
         "transition-delay": {
             "animatable": true,
             "codegen-properties": {
@@ -10663,6 +10680,14 @@
                 "url": "https://www.w3.org/TR/css-animations-1/#typedef-single-animation-play-state"
             }
         },
+        "<transition-behavior-value>": {
+            "grammar": "normal | allow-discrete",
+            "exported": true,
+            "specification": {
+                "category": "css-transitions",
+                "url": "https://drafts.csswg.org/css-transitions-2/#typedef-transition-behavior-value"
+            }
+        },
         "<page-size>": {
             "grammar": "A5 | A4 | A3 | B5 | B4 | letter | legal | ledger",
             "exported": true,

Source/WebCore/css/CSSToStyleMap.cpp

@@ -489,6 +489,14 @@ void CSSToStyleMap::mapAnimationCompositeOperation(Animation& animation, const C
         animation.setCompositeOperation(*compositeOperation);
 }
 
+void CSSToStyleMap::mapAnimationAllowsDiscreteTransitions(Animation& layer, const CSSValue& value)
+{
+    if (treatAsInitialValue(value, CSSPropertyTransitionBehavior))
+        layer.setAllowsDiscreteTransitions(Animation::initialAllowsDiscreteTransitions());
+    else if (is<CSSPrimitiveValue>(value))
+        layer.setAllowsDiscreteTransitions(value.valueID() == CSSValueAllowDiscrete);
+}
+
 void CSSToStyleMap::mapNinePieceImage(const CSSValue* value, NinePieceImage& image)
 {
     // If we're not a value list, then we are "none" and don't need to alter the empty image at all.

Source/WebCore/css/CSSToStyleMap.h

@@ -71,6 +71,7 @@ class CSSToStyleMap {
     static void mapAnimationTimeline(Animation&, const CSSValue&);
     static void mapAnimationTimingFunction(Animation&, const CSSValue&);
     static void mapAnimationCompositeOperation(Animation&, const CSSValue&);
+    static void mapAnimationAllowsDiscreteTransitions(Animation&, const CSSValue&);
 
     void mapNinePieceImage(const CSSValue*, NinePieceImage&);
     static void mapNinePieceImageSlice(const CSSValue&, NinePieceImage&);

Source/WebCore/css/CSSValueKeywords.in

@@ -1744,3 +1744,7 @@ no-autospace
 // auto
 // stable
 both-edges
+
+// transition-behavior
+// normal
+allow-discrete

Source/WebCore/css/ComputedStyleExtractor.cpp

@@ -1434,6 +1434,11 @@ static Ref<CSSValue> fontVariantEastAsianPropertyValue(FontVariantEastAsianVaria
     return CSSValueList::createSpaceSeparated(WTFMove(valueList));
 }
 
+static Ref<CSSPrimitiveValue> valueForTransitionBehavior(bool allowsDiscreteTransitions)
+{
+    return CSSPrimitiveValue::create(allowsDiscreteTransitions ? CSSValueAllowDiscrete : CSSValueNormal);
+}
+
 static Ref<CSSPrimitiveValue> valueForAnimationDuration(double duration)
 {
     return CSSPrimitiveValue::create(duration, CSSUnitType::CSS_S);
@@ -1570,9 +1575,18 @@ static Ref<CSSValue> valueForAnimationTimingFunction(const TimingFunction& timin
     RELEASE_ASSERT_NOT_REACHED();
 }
 
-void ComputedStyleExtractor::addValueForAnimationPropertyToList(CSSValueListBuilder& list, CSSPropertyID property, const Animation* animation)
+enum IsShorthand : bool { No, Yes };
+static void addValueForAnimationPropertyToList(CSSValueListBuilder& list, CSSPropertyID property, const Animation* animation, IsShorthand isShorthand = IsShorthand::No)
 {
-    if (property == CSSPropertyAnimationDuration || property == CSSPropertyTransitionDuration) {
+    if (property == CSSPropertyTransitionBehavior) {
+        if (animation) {
+            if (animation->isAllowsDiscreteTransitionsFilled())
+                return;
+            if (isShorthand == IsShorthand::Yes && animation->allowsDiscreteTransitions() == Animation::initialAllowsDiscreteTransitions())
+                return;
+        }
+        list.append(valueForTransitionBehavior(animation ? animation->allowsDiscreteTransitions() : Animation::initialAllowsDiscreteTransitions()));
+    } else if (property == CSSPropertyAnimationDuration || property == CSSPropertyTransitionDuration) {
         if (!animation || !animation->isDurationFilled())
             list.append(valueForAnimationDuration(animation ? animation->duration() : Animation::initialDuration()));
     } else if (property == CSSPropertyAnimationDelay || property == CSSPropertyTransitionDelay) {
@@ -1619,9 +1633,9 @@ static Ref<CSSValueList> valueListForAnimationOrTransitionProperty(CSSPropertyID
     CSSValueListBuilder list;
     if (animationList) {
         for (auto& animation : *animationList)
-            ComputedStyleExtractor::addValueForAnimationPropertyToList(list, property, animation.ptr());
+            addValueForAnimationPropertyToList(list, property, animation.ptr());
     } else
-        ComputedStyleExtractor::addValueForAnimationPropertyToList(list, property, nullptr);
+        addValueForAnimationPropertyToList(list, property, nullptr);
     return CSSValueList::createCommaSeparated(WTFMove(list));
 }
 
@@ -1631,7 +1645,7 @@ static Ref<CSSValueList> animationShorthandValue(CSSPropertyID property, const A
     auto addAnimation = [&](Ref<Animation> animation) {
         CSSValueListBuilder childList;
         for (auto longhand : shorthandForProperty(property))
-            ComputedStyleExtractor::addValueForAnimationPropertyToList(childList, longhand, animation.ptr());
+            addValueForAnimationPropertyToList(childList, longhand, animation.ptr(), IsShorthand::Yes);
         parentList.append(CSSValueList::createSpaceSeparated(WTFMove(childList)));
     };
     if (animationList && !animationList->isEmpty()) {
@@ -4191,6 +4205,7 @@ RefPtr<CSSValue> ComputedStyleExtractor::valueForPropertyInStyle(const RenderSty
         return computedScale(renderer, style);
     case CSSPropertyRotate:
         return computedRotate(renderer, style);
+    case CSSPropertyTransitionBehavior:
     case CSSPropertyTransitionDelay:
     case CSSPropertyTransitionDuration:
     case CSSPropertyTransitionTimingFunction:

Source/WebCore/css/ComputedStyleExtractor.h

@@ -81,8 +81,6 @@ class ComputedStyleExtractor {
 
     static Ref<CSSPrimitiveValue> currentColorOrValidColor(const RenderStyle&, const StyleColor&);
 
-    static void addValueForAnimationPropertyToList(CSSValueListBuilder&, CSSPropertyID, const Animation*);
-
     static bool updateStyleIfNeededForProperty(Element&, CSSPropertyID);
 
 private: