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

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

 /*
  * 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 347 matching lines @@
   calculateColumnCountAndWidth(newWidth, dummyColumnCount);
   return newWidth != logicalWidth();
 }
 
 bool LayoutMultiColumnFlowThread::isPageLogicalHeightKnown() const {
   if (LayoutMultiColumnSet* columnSet = lastMultiColumnSet())
     return columnSet->isPageLogicalHeightKnown();
   return false;
 }
 
+bool LayoutMultiColumnFlowThread::mayHaveNonUniformPageLogicalHeight() const {
+  const LayoutMultiColumnSet* columnSet = firstMultiColumnSet();
+  if (!columnSet)
+    return false;
+  if (columnSet->nextSiblingMultiColumnSet())
+    return true;
+  return enclosingFragmentationContext();
+}
+
 LayoutSize LayoutMultiColumnFlowThread::flowThreadTranslationAtOffset(
     LayoutUnit offsetInFlowThread,
     PageBoundaryRule rule,
     CoordinateSpaceConversion mode) const {
   if (!hasValidColumnSetInfo())
     return LayoutSize(0, 0);
   LayoutMultiColumnSet* columnSet =
       columnSetAtBlockOffset(offsetInFlowThread, rule);
   if (!columnSet)
     return LayoutSize(0, 0);
@@ skipping 968 matching lines @@
     const {
   return MultiColumnLayoutState(m_lastSetWorkedOn);
 }
 
 void LayoutMultiColumnFlowThread::restoreMultiColumnLayoutState(
     const MultiColumnLayoutState& state) {
   m_lastSetWorkedOn = state.columnSet();
 }
 
 }  // namespace blink