[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/html/HTMLTextFormControlElement.cpp

Index: Source/core/html/HTMLTextFormControlElement.cpp
diff --git a/Source/core/html/HTMLTextFormControlElement.cpp b/Source/core/html/HTMLTextFormControlElement.cpp
index cae2d7932eeb208808342910c0f12a7d2632e33a..f4c2e4bbf94b928bd4d244c13f2c68a2b907e5e8 100644
--- a/Source/core/html/HTMLTextFormControlElement.cpp
+++ b/Source/core/html/HTMLTextFormControlElement.cpp
@@ -640,7 +640,7 @@ String HTMLTextFormControlElement::valueWithHardLineBreaks() const
     return finishText(result);
 }
 
-HTMLTextFormControlElement* enclosingTextFormControl(const Position& position)
+Result<HTMLTextFormControlElement> enclosingTextFormControl(const Position& position)
 {
     ASSERT(position.isNull() || position.anchorType() == Position::PositionIsOffsetInAnchor
         || position.containerNode() || !position.anchorNode()->shadowHost()
@@ -648,9 +648,9 @@ HTMLTextFormControlElement* enclosingTextFormControl(const Position& position)
         
     Node* container = position.containerNode();
     if (!container)
-        return 0;
+        return nullptr;
     Element* ancestor = container->shadowHost();
-    return ancestor && isHTMLTextFormControlElement(ancestor) ? toHTMLTextFormControlElement(ancestor) : 0;
+    return ancestor && isHTMLTextFormControlElement(ancestor) ? toHTMLTextFormControlElement(ancestor) : nullptr;
 }
 
 static const Element* parentHTMLElement(const Element* element)
@@ -690,4 +690,9 @@ void HTMLTextFormControlElement::reportMemoryUsage(MemoryObjectInfo* memoryObjec
     info.addMember(m_textAsOfLastFormControlChangeEvent, "textAsOfLastFormControlChangeEvent");
 }
 
+void HTMLTextFormControlElement::acceptHeapVisitor(Visitor* visitor) const
+{
+    HTMLFormControlElementWithState::acceptHeapVisitor(visitor);
+}
+
 } // namespace Webcore