Improve strut handling in initial column balancing pass.

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/LayoutMultiColumnSet.h"
 
 namespace blink {
 
 // A column balancer traverses a portion of the subtree of a flow thread that
 // belongs to one or more fragmentainer groups within one column set, in order
@@ skipping 207 matching lines @@
   // strut found at a column boundary is the amount of space that we wasted at
   // said column boundary, and it needs to be deducted when estimating the
   // initial balanced column height, or we risk making the column row too tall.
   // An entry set to LayoutUnit::max() means that we didn't detect any object
   // crossing that boundary.
   //
   // [1] http://www.w3.org/TR/css3-break/#parallel-flows
   Vector<LayoutUnit, 32> m_shortestStruts;
 
   LayoutUnit m_tallestUnbreakableLogicalHeight;
+  LayoutUnit m_lastBreakSeen;
 };
 
 // If we have previously used InitialColumnHeightFinder to estimate an initial
 // column height, and that didn't result in tall enough columns, we need
 // subsequent layout passes where we increase the column height by the minimum
 // space shortage at column breaks. This class finds the minimum space shortage
 // after having laid out with the current column height.
 class MinimumSpaceShortageFinder final : public ColumnBalancer {
  public:
   MinimumSpaceShortageFinder(const LayoutMultiColumnSet&,
@@ skipping 23 matching lines @@
 
   // 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