column-span:all in nested multicol requires re-insertion of fragmentainer groups.

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 354 matching lines @@
         }
         LayoutMultiColumnSet* columnSet = toLayoutMultiColumnSet(columnBox);
         layoutScope.setChildNeedsLayout(columnSet);
         if (!m_inBalancingPass) {
             // This is the initial layout pass. We need to reset the column height, because contents
             // typically have changed.
             columnSet->resetColumnHeight();
         }
         if (!m_needsColumnHeightsRecalculation)
             m_needsColumnHeightsRecalculation = columnSet->heightIsAuto();
+        // Since column sets are regular block flow objects, and their position is changed in
+        // regular block layout code (with no means for the multicol code to notice unless we add
+        // hooks there), store the previous position now. If it changes in the imminent layout
+        // pass, we may have to rebalance its columns.
+        columnSet->storeOldPosition();
     }
 
     invalidateColumnSets();
     layout();
 }
 
 bool LayoutMultiColumnFlowThread::recalculateColumnHeights()
 {
     // All column sets that needed layout have now been laid out, so we can finally validate them.
     validateColumnSets();
 
     if (!m_needsColumnHeightsRecalculation)
         return false;
 
     // Column heights may change here because of balancing. We may have to do multiple layout
     // passes, depending on how the contents is fitted to the changed column heights. In most
     // cases, laying out again twice or even just once will suffice. Sometimes we need more
     // passes than that, though, but the number of retries should not exceed the number of
     // columns, unless we have a bug.
     bool needsRelayout = false;
     for (LayoutMultiColumnSet* multicolSet = firstMultiColumnSet(); multicolSet; multicolSet = multicolSet->nextSiblingMultiColumnSet())
-        needsRelayout |= multicolSet->recalculateColumnHeight(m_inBalancingPass ? StretchBySpaceShortage : GuessFromFlowThreadPortion);
+        needsRelayout |= multicolSet->recalculateColumnHeight();
 
     if (needsRelayout)
         setChildNeedsLayout(MarkOnlyThis);
 
     m_inBalancingPass = needsRelayout;
     return needsRelayout;
 }
 
 void LayoutMultiColumnFlowThread::columnRuleStyleDidChange()
 {
@@ skipping 515 matching lines @@
     // First figure out if there's any chance that we're nested at all. If we can be sure that
     // we're not, bail early. This code is run very often, and since locating a containing flow
     // thread has some cost (depending on tree depth), avoid calling enclosingFlowThread() right
     // away. This test may give some false positives (hence the "mayBe"), if we're in an
     // out-of-flow subtree and have an outer multicol container that doesn't affect us, but that's
     // okay. We'll discover that further down the road when trying to locate our enclosing flow
     // thread for real.
     bool mayBeNested = multiColumnBlockFlow()->isInsideFlowThread();
     if (!mayBeNested)
         return;
-    if (!isInInitialLayoutPass()) {
+    LayoutMultiColumnSet* columnSet = columnSetAtBlockOffset(logicalTopInFlowThreadAfterPagination);
+    if (!columnSet)
+        return;
+    if (columnSet->isInitialHeightCalculated()) {
         // We only insert additional fragmentainer groups in the initial layout pass. We only want
         // to balance columns in the last fragmentainer group (if we need to balance at all), so we
         // want that last fragmentainer group to be the same one in all layout passes that follow.
         return;
     }
-    LayoutMultiColumnSet* columnSet = columnSetAtBlockOffset(logicalTopInFlowThreadAfterPagination);
-    if (!columnSet)
-        return;
     MultiColumnFragmentainerGroup& row = columnSet->fragmentainerGroupAtFlowThreadOffset(logicalTopInFlowThreadAfterPagination);
     if (!row.isLastGroup())
         return;
     appendNewFragmentainerGroupIfNeeded(logicalTopInFlowThreadAfterPagination);
 }
 
 }