remove memoryinstrumentation

Source/core/css/FontFeatureValue.h

 /*
  * Copyright (C) 2011 Google 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 26 matching lines @@
     {
         return adoptRef(new FontFeatureValue(tag, value));
     }
 
     const String& tag() const { return m_tag; }
     int value() const { return m_value; }
     String customCssText() const;
 
     bool equals(const FontFeatureValue&) const;
 
-    void reportDescendantMemoryUsage(MemoryObjectInfo*) const;
-
 private:
     FontFeatureValue(const String&, int);
 
     String m_tag;
     const int m_value;
 };
 
 } // namespace
 
 #endif