Add support for flattening in GeometryMapper.

third_party/WebKit/Source/core/layout/LayoutBox.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
@@ skipping 2383 matching lines @@
         toLayoutInline(container)->offsetForInFlowPositionedInline(*this));
   } else if (styleToUse.hasInFlowPosition() && layer()) {
     // Apply the relative position offset when invalidating a rectangle. The
     // layer is translated, but the layout box isn't, so we need to do this to
     // get the right dirty rect.  Since this is called from
     // LayoutObject::setStyle, the relative position flag on the LayoutObject
     // has been cleared, so use the one on the style().
     containerOffset.move(layer()->offsetForInFlowPosition());
   }
 
-  bool preserve3D = container->style()->preserves3D() || style()->preserves3D();
+  bool preserve3D = container->style()->preserves3D();
 
   TransformState::TransformAccumulation accumulation =
       preserve3D ? TransformState::AccumulateTransform
                  : TransformState::FlattenTransform;
 
   if (skipInfo.filterSkipped()) {
     inflateVisualRectForFilterUnderContainer(transformState, *container,
                                              ancestor);
   }
 
@@ skipping 3335 matching lines @@
 
 void LayoutBox::MutableForPainting::
     savePreviousContentBoxSizeAndLayoutOverflowRect() {
   auto& rareData = layoutBox().ensureRareData();
   rareData.m_hasPreviousContentBoxSizeAndLayoutOverflowRect = true;
   rareData.m_previousContentBoxSize = layoutBox().contentBoxRect().size();
   rareData.m_previousLayoutOverflowRect = layoutBox().layoutOverflowRect();
 }
 
 }  // namespace blink