Remove some unused variable assignments

Source/core/platform/ScrollView.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 417 matching lines @@
 
         if (!scrollbarsAreOverlay) {
             // If we ever turn one scrollbar off, always turn the other one off too.  Never ever
             // try to both gain/lose a scrollbar in the same pass.
             if (!newHasHorizontalScrollbar && hasHorizontalScrollbar && vScroll != ScrollbarAlwaysOn)
                 newHasVerticalScrollbar = false;
             if (!newHasVerticalScrollbar && hasVerticalScrollbar && hScroll != ScrollbarAlwaysOn)
                 newHasHorizontalScrollbar = false;
         }
 
-        bool scrollbarIsOverlay = ScrollbarTheme::theme()->usesOverlayScrollbars();
         if (hasHorizontalScrollbar != newHasHorizontalScrollbar) {
             scrollbarExistenceChanged = true;
             if (scrollOrigin().y() && !newHasHorizontalScrollbar && !scrollbarsAreOverlay)
                 ScrollableArea::setScrollOrigin(IntPoint(scrollOrigin().x(), scrollOrigin().y() - m_horizontalScrollbar->height()));
             if (hasHorizontalScrollbar)
                 m_horizontalScrollbar->invalidate();
             setHasHorizontalScrollbar(newHasHorizontalScrollbar);
         }
 
         if (hasVerticalScrollbar != newHasVerticalScrollbar) {
@@ skipping 806 matching lines @@
 {
 }
 
 bool ScrollView::platformIsOffscreen() const
 {
     return false;
 }
 
 
 }