CSSPerspective.toMatrix() should throw if its length is not compatibl…

…e with 'px' unit

https://bugs.webkit.org/show_bug.cgi?id=246891

Reviewed by Antoine Quint.

CSSPerspective.toMatrix() should throw a TypeError if its length is not compatible with 'px' unit:
- https://drafts.css-houdini.org/css-typed-om-1/#dom-csstransformcomponent-tomatrix

* LayoutTests/imported/w3c/web-platform-tests/css/css-typed-om/stylevalue-subclasses/cssTransformComponent-toMatrix-relative-units-expected.txt:
* Source/WebCore/css/typedom/transform/CSSPerspective.cpp:
(WebCore::CSSPerspective::toMatrix):

Canonical link: https://commits.webkit.org/255876@main

LayoutTests/imported/w3c/web-platform-tests/css/css-typed-om/stylevalue-subclasses/cssTransformComponent-toMatrix-relative-units-expected.txt

@@ -1,6 +1,4 @@
 
 PASS CSSTranslate.toMatrix() containing relative units throws TypeError
-FAIL CSSPerspective.toMatrix() containing relative units throws TypeError assert_throws_js: function "() => {
-    return new CSSPerspective(new CSSUnitValue(1, 'em')).toMatrix();
-  }" did not throw
+PASS CSSPerspective.toMatrix() containing relative units throws TypeError
 

Source/WebCore/css/typedom/transform/CSSPerspective.cpp

@@ -148,8 +148,12 @@ ExceptionOr<Ref<DOMMatrix>> CSSPerspective::toMatrix()
     if (!is<CSSUnitValue>(length))
         return Exception { TypeError };
 
+    auto valuePx = downcast<CSSUnitValue>(*length).convertTo(CSSUnitType::CSS_PX);
+    if (!valuePx)
+        return Exception { TypeError, "Length unit is not compatible with 'px'"_s };
+
     TransformationMatrix matrix { };
-    matrix.applyPerspective(downcast<CSSUnitValue>(*length).value());
+    matrix.applyPerspective(valuePx->value());
 
     return { DOMMatrix::create(WTFMove(matrix), DOMMatrixReadOnly::Is2D::No) };
 }