Fix const correctness of containerForRepaint

Source/core/rendering/RenderLayerScrollableArea.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 362 matching lines @@
         layer()->updateLayerPositionsAfterOverflowScroll();
         // Update regions, scrolling may change the clip of a particular region.
         frameView->updateAnnotatedRegions();
         // FIXME: We shouldn't call updateWidgetPositions() here since it might tear down the render tree,
         // for now we just crash to avoid allowing an attacker to use after free.
         frameView->updateWidgetPositions();
         RELEASE_ASSERT(frameView->renderView());
         updateCompositingLayersAfterScroll();
     }
 
-    RenderLayerModelObject* repaintContainer = box().containerForRepaint();
+    const RenderLayerModelObject* repaintContainer = box().containerForRepaint();
     // The caret rect needs to be invalidated after scrolling
     frame->selection().setCaretRectNeedsUpdate();
 
     FloatQuad quadForFakeMouseMoveEvent;
     if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
         quadForFakeMouseMoveEvent = FloatQuad(layer()->renderer()->previousRepaintRect());
     else
         quadForFakeMouseMoveEvent = FloatQuad(layer()->repainter().repaintRect());
 
     quadForFakeMouseMoveEvent = repaintContainer->localToAbsoluteQuad(quadForFakeMouseMoveEvent);
@@ skipping 1170 matching lines @@
 void RenderLayerScrollableArea::setForceNeedsCompositedScrolling(ForceNeedsCompositedScrollingMode mode)
 {
     if (m_forceNeedsCompositedScrolling == mode)
         return;
 
     m_forceNeedsCompositedScrolling = mode;
     layer()->didUpdateNeedsCompositedScrolling();
 }
 
 } // Namespace WebCore