A column-span:all element should always establish a new formatting context.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 4743 matching lines @@
   return node && node->isElementNode() &&
          (toElement(node)->isFormControlElement() ||
           isHTMLImageElement(toElement(node)));
 }
 
 DISABLE_CFI_PERF
 bool LayoutBox::avoidsFloats() const {
   // crbug.com/460704: This should be merged with createsNewFormattingContext().
   return shouldBeConsideredAsReplaced() || hasOverflowClip() || isHR() ||
          isLegend() || isWritingModeRoot() || isFlexItemIncludingDeprecated() ||
+         style()->getColumnSpan() == ColumnSpanAll ||
          style()->containsPaint() || style()->containsLayout() ||
          style()->display() == EDisplay::kFlowRoot;
 }
 
 bool LayoutBox::hasNonCompositedScrollbars() const {
   if (PaintLayerScrollableArea* scrollableArea = this->getScrollableArea()) {
     if (scrollableArea->hasHorizontalScrollbar() &&
         !scrollableArea->layerForHorizontalScrollbar())
       return true;
     if (scrollableArea->hasVerticalScrollbar() &&
@@ skipping 981 matching lines @@
 
 void LayoutBox::MutableForPainting::
     savePreviousContentBoxSizeAndLayoutOverflowRect() {
   auto& rareData = layoutBox().ensureRareData();
   rareData.m_hasPreviousContentBoxSizeAndLayoutOverflowRect = true;
   rareData.m_previousContentBoxSize = layoutBox().contentBoxRect().size();
   rareData.m_previousLayoutOverflowRect = layoutBox().layoutOverflowRect();
 }
 
 }  // namespace blink