Add support for flattening in GeometryMapper.

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

Index: third_party/WebKit/Source/core/layout/LayoutInline.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutInline.cpp b/third_party/WebKit/Source/core/layout/LayoutInline.cpp
index 6992af87ed788db430c335b0b0f57aac83a045ff..4a8cf229152d037e77cd9fec61efc55ee32593ac 100644
--- a/third_party/WebKit/Source/core/layout/LayoutInline.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutInline.cpp
@@ -1211,7 +1211,7 @@ bool LayoutInline::mapToVisualRectInAncestorSpaceInternal(
   if (!container)
     return true;
 
-  bool preserve3D = container->style()->preserves3D() || style()->preserves3D();
+  bool preserve3D = container->style()->preserves3D();

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

I'm not sure that this code has any effect at all, since transforms
can't be put on inlines. Wen I added support last week for 3D to
this method, I cargo culted from mapLocalToAncestor, but now I think
perhaps that method was simply wrong.

 
   TransformState::TransformAccumulation accumulation =
       preserve3D ? TransformState::AccumulateTransform