Disable layout optimization when column height may be non-uniform.

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

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. 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.
@@ skipping 123 matching lines @@
   // is expected to be at the exact top of a column that's known to not have
   // enough space for |contentLogicalHeight|. This method is called when the
   // current column is too short to fit the content, in the hope that there
   // exists one that's tall enough further ahead. If no such column can be
   // found, |flowThreadOffset| will be returned.
   LayoutUnit nextLogicalTopForUnbreakableContent(
       LayoutUnit flowThreadOffset,
       LayoutUnit contentLogicalHeight) const;
 
   virtual bool isPageLogicalHeightKnown() const { return true; }
+  virtual bool mayHaveNonUniformPageLogicalHeight() const = 0;
   bool pageLogicalSizeChanged() const { return m_pageLogicalSizeChanged; }
 
   // Return the visual bounding box based on the supplied flow-thread bounding
   // box. Both rectangles are completely physical in terms of writing mode.
   LayoutRect fragmentsBoundingBox(const LayoutRect& layerBoundingBox) const;
 
   // Convert a logical position in the flow thread coordinate space to a logical
   // position in the containing coordinate space.
   void flowThreadToContainingCoordinateSpace(LayoutUnit& blockPosition,
                                              LayoutUnit& inlinePosition) const;
@@ skipping 48 matching lines @@
 struct ValueToString<LayoutMultiColumnSet*> {
   static String toString(const LayoutMultiColumnSet* value) {
     return String::format("%p", value);
   }
 };
 #endif
 
 }  // namespace blink
 
 #endif  // LayoutFlowThread_h