Oilpan: Validate pointers stored in Member

Source/core/editing/iterators/TextIterator.h

Index: Source/core/editing/iterators/TextIterator.h
diff --git a/Source/core/editing/iterators/TextIterator.h b/Source/core/editing/iterators/TextIterator.h
index 19d9b7bed9ef98c1d93846d34aaf46d9c7e84373..feb162219689fdf1a9cc4ced19c2ece14e58d148 100644
--- a/Source/core/editing/iterators/TextIterator.h
+++ b/Source/core/editing/iterators/TextIterator.h
@@ -164,7 +164,7 @@ private:
     // remaining text box.
     InlineTextBox* m_remainingTextBox;
     // Used to point to LayoutText object for :first-letter.
-    RawPtrWillBeMember<LayoutText> m_firstLetterText;
+    LayoutText* m_firstLetterText;
 
     // Used to do the whitespace collapsing logic.
     RawPtrWillBeMember<Text> m_lastTextNode;