Avoid double hash map look up in SVGElement::updateRelativeLengthsInf…

…ormation()

https://bugs.webkit.org/show_bug.cgi?id=260803

Reviewed by Ryosuke Niwa.

Avoid double hash map look up in SVGElement::updateRelativeLengthsInformation()
and do minor code cleanup.

* Source/WebCore/svg/SVGElement.cpp:
(WebCore::SVGElement::updateRelativeLengthsInformation):

Canonical link: https://commits.webkit.org/267358@main

Source/WebCore/svg/SVGElement.cpp

@@ -1063,16 +1063,13 @@ void SVGElement::updateRelativeLengthsInformation(bool hasRelativeLengths, SVGEl
     if (hasRelativeLengths)
         m_elementsWithRelativeLengths.add(element);
     else {
-        bool neverRegistered = !m_elementsWithRelativeLengths.contains(element);
-        if (neverRegistered)
+        if (!m_elementsWithRelativeLengths.remove(element))
             return;
-
-        m_elementsWithRelativeLengths.remove(element);
     }
 
     if (is<SVGGraphicsElement>(element)) {
-        if (RefPtr parent = parentNode(); is<SVGElement>(parent))
-            downcast<SVGElement>(*parent).updateRelativeLengthsInformation(hasRelativeLengths, *this);
+        if (RefPtr parent = dynamicDowncast<SVGElement>(parentNode()))
+            parent->updateRelativeLengthsInformation(hasRelativeLengths, *this);
     }
 }