Require spanners to have the multicol container as their nearest block formatting context.

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 114 matching lines @@
     LayoutObjectChildList* children() { return &m_children; }
 
     bool beingDestroyed() const { return m_beingDestroyed; }
 
     // These two functions are overridden for inline-block.
     LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const final;
     int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
 
     LayoutUnit minLineHeightForReplacedObject(bool isFirstLine, LayoutUnit replacedHeight) const;
 
+    bool createsNewFormattingContext() const;
+
     const LineBoxList& lineBoxes() const { return m_lineBoxes; }
     LineBoxList* lineBoxes() { return &m_lineBoxes; }
 
     const char* name() const override;
 
 protected:
     InlineFlowBox* firstLineBox() const { return m_lineBoxes.firstLineBox(); }
     InlineFlowBox* lastLineBox() const { return m_lineBoxes.lastLineBox(); }
 
     RootInlineBox* firstRootBox() const { return static_cast<RootInlineBox*>(firstLineBox()); }
@@ skipping 296 matching lines @@
     //
     // If the given offset is at a page boundary, using AssociateWithLatterPage as PageBoundaryRule
     // will move us one page ahead (since the offset is at the top of the "current" page). Using
     // AssociateWithFormerPage instead will keep us where we are (since the offset is at the bottom
     // of the "current" page, which is exactly the same offset as the top offset on the next page).
     //
     // For a page height of 800px, AssociateWithLatterPage will return 1600 if the value passed in
     // is 800. AssociateWithFormerPage will simply return 800.
     LayoutUnit nextPageLogicalTop(LayoutUnit logicalOffset, PageBoundaryRule) const;
 
-    bool createsNewFormattingContext() const;
-
     // Paginated content inside this block was laid out.
     // |logicalTopOffsetAfterPagination| is the logical top offset of the child content after
     // applying any forced or unforced break, if needed.
     void paginatedContentWasLaidOut(LayoutUnit logicalTopOffsetAfterPagination);
 
     // Update minimum page height required to avoid fragmentation where it shouldn't occur (inside
     // unbreakable content, between orphans and widows, etc.). This will be used as a hint to the
     // column balancer to help set a good minimum column height.
     void updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight);
 
@@ skipping 25 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