Remove some unused variable assignments

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 6103 matching lines @@
         return;
 
     FrameView* frameView = frame->view();
     if (!frameView)
         return;
 
     bool isVisibleToHitTest = renderer()->visibleToHitTesting();
     if (HTMLFrameOwnerElement* owner = frame->ownerElement())
         isVisibleToHitTest &= owner->renderer() && owner->renderer()->visibleToHitTesting();
 
-    bool updatedScrollableAreaSet = false;
     if (hasOverflow && isVisibleToHitTest) {
         if (frameView->addScrollableArea(this))
             compositor()->setNeedsUpdateCompositingRequirementsState();
     } else {
         if (frameView->removeScrollableArea(this))
             setNeedsCompositedScrolling(false);
     }
 }
 
 void RenderLayer::updateScrollCornerStyle()
@@ skipping 235 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif