The column balancer should ignore things outside the bounds of the row.

third_party/WebKit/Source/core/layout/LayoutBlock.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 172 matching lines @@
 
     PositionWithAffinity positionForPoint(const LayoutPoint&) override;
 
     LayoutUnit blockDirectionOffset(const LayoutSize& offsetFromBlock) const;
     LayoutUnit inlineDirectionOffset(const LayoutSize& offsetFromBlock) const;
 
     LayoutBlock* blockBeforeWithinSelectionRoot(LayoutSize& offset) const;
 
     void setSelectionState(SelectionState) override;
 
-    LayoutBoxModelObject* virtualContinuation() const final { return continuation(); }
-    bool isAnonymousBlockContinuation() const { return continuation() && isAnonymousBlock(); }
-
-    using LayoutBoxModelObject::continuation;
-    using LayoutBoxModelObject::setContinuation;
-
     static LayoutBlock* createAnonymousWithParentAndDisplay(const LayoutObject*, EDisplay = BLOCK);
     LayoutBlock* createAnonymousBlock(EDisplay display = BLOCK) const { return createAnonymousWithParentAndDisplay(this, display); }
 
     LayoutBox* createAnonymousBoxWithSameTypeAs(const LayoutObject* parent) const override;
 
     int columnGap() const;
 
     // Accessors for logical width/height and margins in the containing block's block-flow direction.
     LayoutUnit logicalWidthForChild(const LayoutBox& child) const { return logicalWidthForChildSize(child.size()); }
     LayoutUnit logicalWidthForChildSize(LayoutSize childSize) const { return isHorizontalWritingMode() ? childSize.width() : childSize.height(); }
@@ skipping 231 matching lines @@
     // FIXME: This is temporary as we move code that accesses block flow
     // member variables out of LayoutBlock and into LayoutBlockFlow.
     friend class LayoutBlockFlow;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlock, isLayoutBlock());
 
 } // namespace blink
 
 #endif // LayoutBlock_h