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

Source/core/editing/TextIterator.h

Index: Source/core/editing/TextIterator.h
diff --git a/Source/core/editing/TextIterator.h b/Source/core/editing/TextIterator.h
index cae9dc5abcfeb684700a3c9690f8d7aa3e23d726..39b11d2c6b9aec798c29d0e741e6a9cca353a9bb 100644
--- a/Source/core/editing/TextIterator.h
+++ b/Source/core/editing/TextIterator.h
@@ -176,7 +176,7 @@ private:
     // remaining text box.
     InlineTextBox* m_remainingTextBox;
     // Used to point to RenderText object for :first-letter.
-    RenderText *m_firstLetterText;
+    RawPtrWillBeMember<RenderText> m_firstLetterText;
 
     // Used to do the whitespace collapsing logic.
     RawPtrWillBeMember<Node> m_lastTextNode;