CSS Keyframes names can't be CSS wide keywords

https://bugs.webkit.org/show_bug.cgi?id=246596
rdar://101226253

Reviewed by Tim Nguyen.

The CSS Animations and CSS Values specifications require identifier-based
keyframes names to not be CSS wide keywords, nor "default", nor "none".

* LayoutTests/imported/w3c/web-platform-tests/css/css-animations/parsing/keyframes-name-invalid-expected.txt:
* Source/WebCore/css/parser/CSSParserImpl.cpp:
(WebCore::CSSParserImpl::consumeKeyframesRule): Forbid the invalid names.

Canonical link: https://commits.webkit.org/255640@main

LayoutTests/imported/w3c/web-platform-tests/css/css-animations/parsing/keyframes-name-invalid-expected.txt

@@ -1,11 +1,11 @@
 
-FAIL invalid: @keyframes none { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes default { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes initial { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes inherit { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes unset { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes revert { } assert_equals: expected 0 but got 1
-FAIL invalid: @keyframes revert-layer { } assert_equals: expected 0 but got 1
+PASS invalid: @keyframes none { }
+PASS invalid: @keyframes default { }
+PASS invalid: @keyframes initial { }
+PASS invalid: @keyframes inherit { }
+PASS invalid: @keyframes unset { }
+PASS invalid: @keyframes revert { }
+PASS invalid: @keyframes revert-layer { }
 PASS invalid: @keyframes 12 { }
 PASS invalid: @keyframes -12 { }
 PASS invalid: @keyframes 12foo { }

Source/WebCore/css/parser/CSSParserImpl.cpp

@@ -648,13 +648,16 @@ RefPtr<StyleRuleKeyframes> CSSParserImpl::consumeKeyframesRule(CSSParserTokenRan
     if (!prelude.atEnd())
         return nullptr; // Parse error; expected single non-whitespace token in @keyframes header
 
-    AtomString name;
     if (nameToken.type() == IdentToken) {
-        name = nameToken.value().toAtomString();
-    } else if (nameToken.type() == StringToken)
-        name = nameToken.value().toAtomString();
-    else
-        return nullptr; // Parse error; expected ident token in @keyframes header
+        // According to the CSS Values specification, identifier-based keyframe names
+        // are not allowed to be CSS wide keywords or "default". And CSS Animations 
+        // additionally excludes the "none" keyword.
+        if (!isValidCustomIdentifier(nameToken.id()) || nameToken.id() == CSSValueNone)
+            return nullptr;
+    } else if (nameToken.type() != StringToken)
+        return nullptr; // Parse error; expected ident token or string in @keyframes header
+
+    auto name = nameToken.value().toAtomString();
 
     if (m_observerWrapper) {
         m_observerWrapper->observer().startRuleHeader(StyleRuleType::Keyframes, m_observerWrapper->startOffset(rangeCopy));