Get rid of HitTestChildBlockBackground walk.

sky/engine/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 978 matching lines @@
     // Begin by walking our list of positive layers from highest z-index down to the lowest z-index.
     RenderLayer* hitLayer = hitTestChildren(PositiveZOrderChildren, rootLayer, request, result, hitTestRect, hitTestLocation,
                                         localTransformState.get(), zOffsetForDescendantsPtr, zOffset, unflattenedTransformState.get(), depthSortDescendants);
     if (hitLayer) {
         if (!depthSortDescendants)
             return hitLayer;
         candidateLayer = hitLayer;
     }
 
     // Now check our overflow objects.
+    // TODO(ojan): This call has no test coverage.
     hitLayer = hitTestChildren(NormalFlowChildren, rootLayer, request, result, hitTestRect, hitTestLocation,
                            localTransformState.get(), zOffsetForDescendantsPtr, zOffset, unflattenedTransformState.get(), depthSortDescendants);
     if (hitLayer) {
         if (!depthSortDescendants)
             return hitLayer;
         candidateLayer = hitLayer;
     }
 
     LayoutRect layerBounds;
     ClipRect backgroundRect, foregroundRect;
@@ skipping 414 matching lines @@
     }
 }
 
 void showLayerTree(const blink::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif