Always lay out the flow thread when the multicol container is laid out.

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

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 157 matching lines @@
     virtual bool needsNewWidth() const;
 
     bool isPageLogicalHeightKnown() const final;
 
     LayoutSize flowThreadTranslationAtOffset(LayoutUnit) const;
 
     LayoutPoint visualPointToFlowThreadPoint(const LayoutPoint& visualPoint) const override;
 
     LayoutMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const final;
 
-    void layoutColumns(bool relayoutChildren, SubtreeLayoutScope&);
+    void layoutColumns(SubtreeLayoutScope&);
 
     bool isInInitialLayoutPass() const { return !m_inBalancingPass; }
 
     // Skip past a column spanner during flow thread layout. Spanners are not laid out inside the
     // flow thread, since the flow thread is not in a spanner's containing block chain (since the
     // containing block is the multicol container).
     void skipColumnSpanner(LayoutBox*, LayoutUnit logicalTopInFlowThread);
 
     bool recalculateColumnHeights();
 
@@ skipping 58 matching lines @@
     bool m_isBeingEvacuated;
 };
 
 // Cannot use DEFINE_LAYOUT_OBJECT_TYPE_CASTS here, because isMultiColumnFlowThread() is defined in
 // LayoutFlowThread, not in LayoutObject.
 DEFINE_TYPE_CASTS(LayoutMultiColumnFlowThread, LayoutFlowThread, object, object->isLayoutMultiColumnFlowThread(), object.isLayoutMultiColumnFlowThread());
 
 } // namespace blink
 
 #endif // LayoutMultiColumnFlowThread_h