Shift flowthread-to-visual coordinate space conversion one level up in the tree.

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/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2250 matching lines @@
         } else if (o->isBox()) {
             if (o->style()->isFlippedBlocksWritingMode()) {
                 IntPoint centerPoint = roundedIntPoint(transformState.mappedPoint());
                 transformState.move(toLayoutBox(o)->flipForWritingMode(LayoutPoint(centerPoint)) - centerPoint);
             }
             mode &= ~ApplyContainerFlip;
         }
     }
 
     LayoutSize containerOffset = offsetFromContainer(o);
-    if (o->isLayoutFlowThread()) {
+    if (isLayoutFlowThread()) {
         // So far the point has been in flow thread coordinates (i.e. as if everything in
         // the fragmentation context lived in one tall single column). Convert it to a
-        // visual point now.
-        LayoutPoint pointInContainer = roundedLayoutPoint(transformState.mappedPoint()) + containerOffset;
-        containerOffset += o->columnOffset(pointInContainer);
+        // visual point now, since we're about to escape the flow thread.
+        containerOffset += columnOffset(roundedLayoutPoint(transformState.mappedPoint()));
     }
 
     // Text objects just copy their parent's computed style, so we need to ignore them.
     bool preserve3D = mode & UseTransforms && ((o->style()->preserves3D() && !o->isText()) || (style()->preserves3D() && !isText()));
     if (mode & UseTransforms && shouldUseTransformFromContainer(o)) {
         TransformationMatrix t;
         getTransformFromContainer(o, containerOffset, t);
         transformState.applyTransform(t, preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
     } else {
         transformState.move(containerOffset.width(), containerOffset.height(), preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
@@ skipping 1440 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif