perspective calc() values aren't clipped to 0

https://bugs.webkit.org/show_bug.cgi?id=249151

Reviewed by Simon Fraser and Dean Jackson.

The "perspective" property is specified to only allow non-negative values,
see https://www.w3.org/TR/css-transforms-2/#perspective-property. However,
we don't clip values that are computed to less than 0, for instance using a
calc() expression. Instead, we deem them invalid internally and thus consider
as if "none" was provided, which has implications when blending. Indeed, when
interpolating between a valid value and "none", we use discrete interpolation.

We now correctly clip values below 0.

Note that the relevant WPT test still fails, because the test itself is not
valid. It is being addressed in a dedicated WPT PR and will be imported back
into WebKit yielding a PASS result. See web-platform-tests/wpt#37457.

* LayoutTests/imported/w3c/web-platform-tests/css/css-typed-om/the-stylepropertymap/properties/perspective-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/web-animations/responsive/perspective-expected.txt:
* Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp:
(WebCore::CSSPropertyParserHelpers::consumePerspective):

Canonical link: https://commits.webkit.org/257779@main

LayoutTests/imported/w3c/web-platform-tests/css/css-typed-om/the-stylepropertymap/properties/perspective-expected.txt

@@ -6,7 +6,7 @@ PASS Can set 'perspective' to CSS-wide keywords: revert
 FAIL Can set 'perspective' to var() references:  var(--A) assert_equals: expected 2 but got 1
 PASS Can set 'perspective' to the 'none' keyword: none
 PASS Can set 'perspective' to a length: 0px
-FAIL Can set 'perspective' to a length: -3.14em assert_class_string: relative lengths must compute to a CSSUnitValue expected "[object CSSUnitValue]" but got "[object CSSKeywordValue]"
+PASS Can set 'perspective' to a length: -3.14em
 PASS Can set 'perspective' to a length: 3.14cm
 FAIL Can set 'perspective' to a length: calc(0px + 0em) assert_equals: expected "px" but got "em"
 PASS Setting 'perspective' to a percent throws TypeError

LayoutTests/imported/w3c/web-platform-tests/web-animations/responsive/perspective-expected.txt

@@ -1,5 +1,5 @@
 
 PASS perspective responsive to style changes
-FAIL perspective clamped to 0px assert_equals: expected "0px" but got "100px"
+FAIL perspective clamped to 0px assert_equals: expected "0px" but got "20px"
 FAIL perspective responsive to inherited changes assert_equals: expected "80px" but got "none"
 

Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp

@@ -6569,13 +6569,7 @@ RefPtr<CSSValue> consumePerspective(CSSParserTokenRange& range, CSSParserMode cs
 {
     if (range.peek().id() == CSSValueNone)
         return consumeIdent(range);
-
-    if (auto parsedValue = consumeLength(range, cssParserMode, ValueRange::All)) {
-        if (!parsedValue->isNegative().value_or(false))
-            return parsedValue;
-    }
-
-    return nullptr;
+    return consumeLength(range, cssParserMode, ValueRange::NonNegative);
 }
 
 RefPtr<CSSValue> consumeScrollSnapAlign(CSSParserTokenRange& range)