Get rid of loops looking for the first Element ancestor

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 0253525e3481a27a63fbedffb0bd68d3fdddb7af..1563af9a1beae961f203e482c01b42a5d6d5cbf7 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -2277,12 +2277,12 @@ Node* Element::insertAdjacent(const String& where, Node* newChild, ExceptionStat
 static Element* contextElementForInsertion(const String& where, Element* element, ExceptionState& exceptionState)
 {
     if (equalIgnoringCase(where, "beforeBegin") || equalIgnoringCase(where, "afterEnd")) {
-        ContainerNode* parent = element->parentNode();
-        if (!parent || !parent->isElementNode()) {
+        Element* parent = element->parentElement();
+        if (!parent) {
             exceptionState.throwDOMException(NoModificationAllowedError, "The element has no parent.");
             return 0;
         }
-        return toElement(parent);
+        return parent;
     }
     if (equalIgnoringCase(where, "afterBegin") || equalIgnoringCase(where, "beforeEnd"))
         return element;