InitialColumnHeightFinder needs to take all expected rows into account.

third_party/WebKit/Source/core/layout/LayoutMultiColumnSet.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 89 matching lines @@
            LayoutBlockFlow::isOfType(type);
   }
   bool canHaveChildren() const final { return false; }
 
   // Return the width and height of a single column or page in the set.
   LayoutUnit pageLogicalWidth() const { return flowThread()->logicalWidth(); }
   LayoutUnit pageLogicalHeightForOffset(LayoutUnit) const;
   LayoutUnit pageRemainingLogicalHeightForOffset(LayoutUnit,
                                                  PageBoundaryRule) const;
   bool isPageLogicalHeightKnown() const;
+
+  // Return true if there's nothing with the current state of column balancing
+  // that prevents us from inserting additional fragmentainer groups, if needed.
+  bool newFragmentainerGroupsAllowed() const;
+
   LayoutUnit tallestUnbreakableLogicalHeight() const {
     return m_tallestUnbreakableLogicalHeight;
   }
   void propagateTallestUnbreakableLogicalHeight(LayoutUnit value) {
     m_tallestUnbreakableLogicalHeight =
         std::max(value, m_tallestUnbreakableLogicalHeight);
   }
 
   LayoutUnit nextLogicalTopForUnbreakableContent(
       LayoutUnit flowThreadOffset,
@@ skipping 148 matching lines @@
   LayoutUnit m_oldLogicalTop;
 
   bool m_initialHeightCalculated;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutMultiColumnSet, isLayoutMultiColumnSet());
 
 }  // namespace blink
 
 #endif  // LayoutMultiColumnSet_h