Adopt more smart pointers in mathml

https://bugs.webkit.org/show_bug.cgi?id=274388

Reviewed by Sihui Liu.

Adopt more smart pointers in mathml based on the
[alpha.webkit.UncountedLocalVarsChecker] warning.

* Source/WebCore/mathml/MathMLAnnotationElement.cpp:
(WebCore::MathMLAnnotationElement::attributeChanged):
* Source/WebCore/mathml/MathMLElement.cpp:
(WebCore::MathMLElement::defaultEventHandler):
* Source/WebCore/mathml/MathMLRowElement.cpp:
(WebCore::MathMLRowElement::childrenChanged):
* Source/WebCore/mathml/MathMLSelectElement.cpp:
(WebCore::MathMLSelectElement::MathMLSelectElement):
(WebCore::MathMLSelectElement::getSelectedActionChild):
(WebCore::MathMLSelectElement::getSelectedSemanticsChild):

Canonical link: https://commits.webkit.org/279070@main

Source/WebCore/mathml/MathMLAnnotationElement.cpp

@@ -78,7 +78,7 @@ bool MathMLAnnotationElement::childShouldCreateRenderer(const Node& child) const
 void MathMLAnnotationElement::attributeChanged(const QualifiedName& name, const AtomString& oldValue, const AtomString& newValue, AttributeModificationReason reason)
 {
     if (name == MathMLNames::srcAttr || name == MathMLNames::encodingAttr) {
-        auto* parent = parentElement();
+        RefPtr parent = parentElement();
         if (is<MathMLElement>(parent) && parent->hasTagName(semanticsTag))
             downcast<MathMLElement>(*parent).updateSelectedChild();
     }

Source/WebCore/mathml/MathMLElement.cpp

@@ -246,8 +246,8 @@ void MathMLElement::defaultEventHandler(Event& event)
         if (MouseEvent::canTriggerActivationBehavior(event)) {
             const auto& href = attributeWithoutSynchronization(hrefAttr);
             event.setDefaultHandled();
-            if (auto* frame = document().frame())
-                frame->loader().changeLocation(document().completeURL(href), selfTargetFrameName(), &event, ReferrerPolicy::EmptyString, document().shouldOpenExternalURLsPolicyToPropagate());
+            if (RefPtr frame = document().frame())
+                frame->checkedLoader()->changeLocation(document().completeURL(href), selfTargetFrameName(), &event, ReferrerPolicy::EmptyString, document().shouldOpenExternalURLsPolicyToPropagate());
             return;
         }
     }

Source/WebCore/mathml/MathMLRowElement.cpp

@@ -54,9 +54,9 @@ Ref<MathMLRowElement> MathMLRowElement::create(const QualifiedName& tagName, Doc
 
 void MathMLRowElement::childrenChanged(const ChildChange& change)
 {
-    for (auto child = firstChild(); child; child = child->nextSibling()) {
+    for (RefPtr child = firstChild(); child; child = child->nextSibling()) {
         if (child->hasTagName(moTag))
-            static_cast<MathMLOperatorElement*>(child)->setOperatorFormDirty();
+            static_cast<MathMLOperatorElement*>(child.get())->setOperatorFormDirty();
     }
 
     MathMLPresentationElement::childrenChanged(change);

Source/WebCore/mathml/MathMLSelectElement.cpp

@@ -47,7 +47,6 @@ using namespace MathMLNames;
 
 MathMLSelectElement::MathMLSelectElement(const QualifiedName& tagName, Document& document)
     : MathMLRowElement(tagName, document)
-    , m_selectedChild(nullptr)
 {
 }
 
@@ -134,9 +133,9 @@ Element* MathMLSelectElement::getSelectedActionChild()
 {
     ASSERT(hasTagName(mactionTag));
 
-    auto* child = firstElementChild();
+    RefPtr child = firstElementChild();
     if (!child)
-        return child;
+        return nullptr;
 
     // The value of the actiontype attribute is case-sensitive.
     auto& actiontype = attributeWithoutSynchronization(MathMLNames::actiontypeAttr);
@@ -148,17 +147,19 @@ Element* MathMLSelectElement::getSelectedActionChild()
         { }
     } else {
         // For the "toggle" action type or any unknown action type, we rely on the value of the selection attribute to determine the visible child.
-        getSelectedActionChildAndIndex(child);
+        Element* selectedChild;
+        getSelectedActionChildAndIndex(selectedChild);
+        child = selectedChild;
     }
 
-    return child;
+    return child.get();
 }
 
 Element* MathMLSelectElement::getSelectedSemanticsChild()
 {
     ASSERT(hasTagName(semanticsTag));
 
-    auto* child = firstElementChild();
+    RefPtr child = firstElementChild();
     if (!child)
         return nullptr;
 
@@ -167,7 +168,7 @@ Element* MathMLSelectElement::getSelectedSemanticsChild()
         child = child->nextElementSibling();
     } else if (!downcast<MathMLElement>(*child).isSemanticAnnotation()) {
         // The first child is a presentation MathML but not an annotation, so we can just display it.
-        return child;
+        return child.get();
     }
     // Otherwise, the first child is an <annotation> or <annotation-xml> element. This is invalid, but some people use this syntax so we take care of this case too and start the search from this first child.
 
@@ -180,7 +181,7 @@ Element* MathMLSelectElement::getSelectedSemanticsChild()
             if (child->hasAttributeWithoutSynchronization(MathMLNames::srcAttr))
                 continue;
             // Otherwise, we assume it is a text annotation that can always be displayed and we stop here.
-            return child;
+            return child.get();
         }
 
         if (child->hasTagName(MathMLNames::annotation_xmlTag)) {
@@ -190,7 +191,7 @@ Element* MathMLSelectElement::getSelectedSemanticsChild()
             // If the <annotation-xml> element has an encoding attribute describing presentation MathML, SVG or HTML we assume the content can be displayed and we stop here.
             auto& value = child->attributeWithoutSynchronization(MathMLNames::encodingAttr);
             if (isMathMLEncoding(value) || isSVGEncoding(value) || isHTMLEncoding(value))
-                return child;
+                return child.get();
         }
     }