Oilpan: add [WillBeGarbageCollected] for Element.

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 43367b4fdaf6f869b4dca4d4241b313c8bc5dd76..246dc0a661e42fd5089970bf7bd77a4c73a6a42c 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -2231,7 +2231,7 @@ void Element::setOuterHTML(const String& html, ExceptionState& exceptionState)
         return;
     }
 
-    RefPtr<Element> parent = toElement(p);
+    RefPtrWillBeRawPtr<Element> parent = toElement(p);
     RefPtr<Node> prev = previousSibling();
     RefPtr<Node> next = nextSibling();
 
@@ -2318,7 +2318,7 @@ void Element::insertAdjacentText(const String& where, const String& text, Except
 
 void Element::insertAdjacentHTML(const String& where, const String& markup, ExceptionState& exceptionState)
 {
-    RefPtr<Element> contextElement = contextElementForInsertion(where, this, exceptionState);
+    RefPtrWillBeRawPtr<Element> contextElement = contextElementForInsertion(where, this, exceptionState);
     if (!contextElement)
         return;