Mac: Delete now-dead elastic overscroll code

Source/platform/scroll/ScrollTypes.h

 /*
  * Copyright (C) 2006 Apple Computer, 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 94 matching lines @@
 }
 
 enum ScrollGranularity {
     ScrollByLine,
     ScrollByPage,
     ScrollByDocument,
     ScrollByPixel,
     ScrollByPrecisePixel
 };
 
-enum ScrollElasticity {
-    ScrollElasticityAutomatic,
-    ScrollElasticityNone,
-    ScrollElasticityAllowed
-};
-
 enum ScrollbarOrientation { HorizontalScrollbar, VerticalScrollbar };
 
 enum ScrollbarMode { ScrollbarAuto, ScrollbarAlwaysOff, ScrollbarAlwaysOn };
 
 enum ScrollbarControlSize { RegularScrollbar, SmallScrollbar };
 
 typedef unsigned ScrollbarControlState;
 
 enum ScrollbarControlStateMask {
     ActiveScrollbarState = 1,
@@ skipping 57 matching lines @@
     bool didScroll;
     float unusedScrollDeltaX;
     float unusedScrollDeltaY;
 };
 
 typedef unsigned ScrollbarControlPartMask;
 
 }
 
 #endif