Remove trace() methods for stack-only classes.

third_party/WebKit/Source/core/editing/SelectionModifier.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 39 matching lines @@
   LayoutUnit xPosForVerticalArrowNavigation() const {
     return m_xPosForVerticalArrowNavigation;
   }
   const VisibleSelection& selection() const { return m_selection; }
 
   bool modify(EAlteration, SelectionDirection, TextGranularity);
   bool modifyWithPageGranularity(EAlteration,
                                  unsigned verticalDistance,
                                  VerticalDirection);
 
-  DECLARE_VIRTUAL_TRACE();
-
  private:
   // TODO(yosin): We should move |EPositionType| to "SelectionModifier.cpp",
   // it is only used for implementing |modify()|.
   // TODO(yosin) We should use capitalized name for |EPositionType|.
   enum EPositionType { START, END, BASE, EXTENT };  // NOLINT
 
   LocalFrame* frame() const { return m_frame; }
 
   TextDirection directionOfEnclosingBlock() const;
   TextDirection directionOfSelection() const;
@@ skipping 17 matching lines @@
   LayoutUnit m_xPosForVerticalArrowNavigation;
 
   DISALLOW_COPY_AND_ASSIGN(SelectionModifier);
 };
 
 LayoutUnit NoXPosForVerticalArrowNavigation();
 
 }  // namespace blink
 
 #endif  // SelectionModifier_h