No reason to prevent subpixel column heights in the initial height calculation.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/MultiColumnFragmentainerGroup.h"
 
 namespace blink {
 
 // A column balancer traverses the portion of the subtree of a flow thread that belongs to a given
 // fragmentainer group, in order to collect certain data to be used for column balancing. This is an
@@ skipping 122 matching lines @@
             , m_assumedImplicitBreaks(0) { }
 
         unsigned assumedImplicitBreaks() const { return m_assumedImplicitBreaks; }
         void assumeAnotherImplicitBreak() { m_assumedImplicitBreaks++; }
         LayoutUnit breakOffset() const { return m_breakOffset; }
 
         // Return the column height that this content run would require, considering the implicit
         // breaks assumed so far.
         LayoutUnit columnLogicalHeight(LayoutUnit startOffset) const
         {
-            // TODO(leviw): This should probably be fromFloatCeil.
-            return LayoutUnit(ceilf((m_breakOffset - startOffset) / float(m_assumedImplicitBreaks + 1)));
+            return LayoutUnit::fromFloatCeil(float(m_breakOffset - startOffset) / float(m_assumedImplicitBreaks + 1));
         }
 
     private:
         LayoutUnit m_breakOffset; // Flow thread offset where this run ends.
         unsigned m_assumedImplicitBreaks; // Number of implicit breaks in this run assumed so far.
     };
     Vector<ContentRun, 32> m_contentRuns;
 
     // Shortest strut found at each column boundary (index 0 being the boundary between the first
     // and the second column, index 1 being the one between the second and the third boundary, and
@@ skipping 40 matching lines @@
     LayoutUnit m_minimumSpaceShortage;
 
     // Set when breaking before a block, and we're looking for the first unbreakable descendant, in
     // order to report correct space shortage for that one.
     LayoutUnit m_pendingStrut;
 
     unsigned m_forcedBreaksCount;
 };
 
 } // namespace blink