Revert of Oilpan: Prepare to move RenderObject and RenderObjectChildList to Oilpan heap.

Source/core/rendering/RenderObjectChildList.cpp

Index: Source/core/rendering/RenderObjectChildList.cpp
diff --git a/Source/core/rendering/RenderObjectChildList.cpp b/Source/core/rendering/RenderObjectChildList.cpp
index 0a9798bcdeb520ece2b2873c0cc4f8697ffc53d6..6a5e74f0f7ecd9d79d4b924fb1c61fb2dde3ea57 100644
--- a/Source/core/rendering/RenderObjectChildList.cpp
+++ b/Source/core/rendering/RenderObjectChildList.cpp
@@ -34,12 +34,6 @@
 #include "core/rendering/style/RenderStyle.h"
 
 namespace blink {
-
-void RenderObjectChildList::trace(Visitor* visitor)
-{
-    visitor->trace(m_firstChild);
-    visitor->trace(m_lastChild);
-}
 
 void RenderObjectChildList::destroyLeftoverChildren()
 {