[css-properties-values-api] non-inherited custom property fails to in…

…herit from parent when "inherit" is set

https://bugs.webkit.org/show_bug.cgi?id=251590

Reviewed by Antti Koivisto.

We would only look at the map of inherited custom properties when applying the "inherit" value
for a custom property. However, a non-inherited value should also use its parent's value in that
case.

* LayoutTests/imported/w3c/web-platform-tests/css/css-properties-values-api/registered-properties-inheritance-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/css/css-properties-values-api/registered-properties-inheritance.html:
* Source/WebCore/style/StyleBuilderCustom.h:
(WebCore::Style::BuilderCustom::applyInheritCustomProperty):

Canonical link: https://commits.webkit.org/259809@main

LayoutTests/imported/w3c/web-platform-tests/css/css-properties-values-api/registered-properties-inheritance-expected.txt

@@ -2,6 +2,7 @@
 PASS Registered properties are correctly inherited (or not) depending on the inherits flag.
 PASS Explicitly inheriting from a parent with an invalid value results in initial value.
 PASS Explicitly inheriting from a parent with no value results in initial value.
+PASS Explicitly inheriting from a parent with a value results in that value.
 PASS Reference to undefined variable results in inherited value
 PASS Reference to syntax-incompatible variable results in inherited value
 PASS Font-relative units are absolutized before before inheritance

LayoutTests/imported/w3c/web-platform-tests/css/css-properties-values-api/registered-properties-inheritance.html

@@ -58,6 +58,13 @@
     assert_equals(getComputedStyle(inner).getPropertyValue('--initial-length-2'), '0px');
 }, "Explicitly inheriting from a parent with no value results in initial value.");
 
+test(function(){
+    CSS.registerProperty({name: '--initial-length-3', syntax: '<length>', initialValue: '0px', inherits: false});
+    outer.style = '--initial-length-3: 100px';
+    inner.style = '--initial-length-3: inherit';
+    assert_equals(getComputedStyle(inner).getPropertyValue('--initial-length-3'), '100px');
+}, "Explicitly inheriting from a parent with a value results in that value.");
+
 test(function(){
     CSS.registerProperty({name: '--inherited-length-4', syntax: '<length>', initialValue: '0px', inherits: true});
     outer.style = '--inherited-length-4: 42px';

Source/WebCore/style/StyleBuilderCustom.h

@@ -2167,6 +2167,8 @@ inline void BuilderCustom::applyInheritCustomProperty(BuilderState& builderState
     auto* parentValue = builderState.parentStyle().inheritedCustomProperties().get(name);
     if (parentValue && !(registered && !registered->inherits))
         applyValueCustomProperty(builderState, registered, const_cast<CSSCustomPropertyValue&>(*parentValue));
+    else if (auto* nonInheritedParentValue = builderState.parentStyle().nonInheritedCustomProperties().get(name))
+        applyValueCustomProperty(builderState, registered, const_cast<CSSCustomPropertyValue&>(*nonInheritedParentValue));
     else
         applyInitialCustomProperty(builderState, registered, name);
 }