Oilpan: Replace RefPtrs to Node and its subclasses in core/html with Oilpan transitin types.

Source/core/html/HTMLPlugInElement.cpp

Index: Source/core/html/HTMLPlugInElement.cpp
diff --git a/Source/core/html/HTMLPlugInElement.cpp b/Source/core/html/HTMLPlugInElement.cpp
index dc6eb1df7c1b4de1486c439570acf92d388c539c..ba7f10ff3e4155fa9c224af326ed089594a4cbde 100644
--- a/Source/core/html/HTMLPlugInElement.cpp
+++ b/Source/core/html/HTMLPlugInElement.cpp
@@ -135,7 +135,7 @@ void HTMLPlugInElement::attach(const AttachContext& context)
 
 void HTMLPlugInElement::updateWidget()
 {
-    RefPtr<HTMLPlugInElement> protector(this);
+    RefPtrWillBeRawPtr<HTMLPlugInElement> protector(this);
     updateWidgetInternal();
     if (m_isDelayingLoadEvent) {
         m_isDelayingLoadEvent = false;