Remove backface visibility

sky/engine/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 619 matching lines @@
             localHitTestLocation = HitTestLocation(localPoint);
 
         // Now do a hit test with the root layer shifted to be us.
         rootLayer = layer();
     }
 
     // Ensure our lists and 3d status are up-to-date.
     layer()->stackingNode()->updateLayerListsIfNeeded();
     layer()->update3DTransformedDescendantStatus();
 
-    // Check for hit test on backface if backface-visibility is 'hidden'
-    if (localTransformState && style()->backfaceVisibility() == BackfaceVisibilityHidden) {
-        TransformationMatrix invertedMatrix = localTransformState->m_accumulatedTransform.inverse();
-        // If the z-vector of the matrix is negative, the back is facing towards the viewer.
-        if (invertedMatrix.m33() < 0)
-            return 0;
-    }
-
     RefPtr<HitTestingTransformState> unflattenedTransformState = localTransformState;
     if (localTransformState && !style()->preserves3D()) {
         // Keep a copy of the pre-flattening state, for computing z-offsets for the container
         unflattenedTransformState = HitTestingTransformState::create(*localTransformState);
         // This layer is flattening, so flatten the state passed to descendants.
         localTransformState->flatten();
     }
 
     // The following are used for keeping track of the z-depth of the hit point of 3d-transformed
     // descendants.
@@ skipping 2412 matching lines @@
 
 RenderBox::BoxDecorationData::BoxDecorationData(const RenderStyle& style)
 {
     backgroundColor = style.colorIncludingFallback(CSSPropertyBackgroundColor);
     hasBackground = backgroundColor.alpha() || style.hasBackgroundImage();
     ASSERT(hasBackground == style.hasBackground());
     hasBorder = style.hasBorder();
 }
 
 } // namespace blink