Oilpan: Replace RefPtrs to Node and its subclasses in core/rendering with Oilpan transition types.

Source/core/rendering/RenderWidget.cpp

Index: Source/core/rendering/RenderWidget.cpp
diff --git a/Source/core/rendering/RenderWidget.cpp b/Source/core/rendering/RenderWidget.cpp
index 50cd0693c0fde230e9160af1f48f0da21d1910b8..d31cf80e356ed25f0cfd8b58ce95a06bc5e4af9f 100644
--- a/Source/core/rendering/RenderWidget.cpp
+++ b/Source/core/rendering/RenderWidget.cpp
@@ -110,7 +110,7 @@ bool RenderWidget::setWidgetGeometry(const LayoutRect& frame)
         return false;
 
     RefPtr<RenderWidget> protector(this);
-    RefPtr<Node> protectedNode(node());
+    RefPtrWillBeRawPtr<Node> protectedNode(node());
     widget->setFrameRect(newFrame);
     return widget->frameRect().size() != newFrame.size();
 }