Add support for flattening in GeometryMapper.

third_party/WebKit/Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved.
  *               (http://www.torchmobile.com/)
@@ skipping 1287 matching lines @@
       LayoutBox* parentBox = toLayoutBox(parent);
 
       // Never flip for SVG as it handles writing modes itself.
       if (!isSVG()) {
         transformState.flatten();
         LayoutRect rect(transformState.lastPlanarQuad().boundingBox());
         parentBox->flipForWritingMode(rect);
         transformState.setQuad(FloatQuad(FloatRect(rect)));
       }
 
-      bool preserve3D = (parent->style()->preserves3D() && !parent->isText()) ||
-                        (style()->preserves3D() && !isText());
+      bool preserve3D = parent->style()->preserves3D() && !parent->isText();

[chrishtr, 2017/03/10 23:29:54]

Ditto here about whether this code has any use - is it for SVG children maybe?

 
       TransformState::TransformAccumulation accumulation =
           preserve3D ? TransformState::AccumulateTransform
                      : TransformState::FlattenTransform;
 
       if (parent != ancestor &&
           !parentBox->mapScrollingContentsRectToBoxSpace(
               transformState, accumulation, visualRectFlags))
         return false;
     }
@@ skipping 2274 matching lines @@
     const blink::LayoutObject* root = object1;
     while (root->parent())
       root = root->parent();
     root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
   } else {
     WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
   }
 }
 
 #endif