Update outer flow thread membership before changing multicolness.

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
  * modify it under the terms of the GNU Library General Public
@@ skipping 139 matching lines @@
     }
 
     if (isOutOfFlowPositioned())
         LayoutBlock::removePositionedObject(this);
 }
 
 void LayoutBox::styleWillChange(StyleDifference diff, const ComputedStyle& newStyle)
 {
     const ComputedStyle* oldStyle = style();
     if (oldStyle) {
+        LayoutFlowThread* flowThread = flowThreadContainingBlock();
+        if (flowThread && flowThread != this)
+            flowThread->flowThreadDescendantStyleWillChange(this, diff, newStyle);
+
         // The background of the root element or the body element could propagate up to
         // the canvas. Just dirty the entire canvas when our style changes substantially.
         if ((diff.needsPaintInvalidation() || diff.needsLayout()) && node()
             && (isHTMLHtmlElement(*node()) || isHTMLBodyElement(*node()))) {
             view()->setShouldDoFullPaintInvalidation();
 
             if (oldStyle->hasEntirelyFixedBackground() != newStyle.hasEntirelyFixedBackground())
                 view()->compositor()->setNeedsUpdateFixedBackground();
         }
 
@@ skipping 66 matching lines @@
         document().view()->recalculateScrollbarOverlayStyle();
         document().view()->recalculateCustomScrollbarStyle();
     }
     updateShapeOutsideInfoAfterStyleChange(*style(), oldStyle);
     updateGridPositionAfterStyleChange(oldStyle);
 
     if (LayoutMultiColumnSpannerPlaceholder* placeholder = this->spannerPlaceholder())
         placeholder->layoutObjectInFlowThreadStyleDidChange(oldStyle);
 
     updateSlowRepaintStatusAfterStyleChange();
+
+    if (oldStyle) {
+        LayoutFlowThread* flowThread = flowThreadContainingBlock();
+        if (flowThread && flowThread != this)
+            flowThread->flowThreadDescendantStyleDidChange(this, diff, *oldStyle);
+    }
 }
 
 void LayoutBox::updateSlowRepaintStatusAfterStyleChange()
 {
     if (!frameView())
         return;
 
     // On low-powered/mobile devices, preventing blitting on a scroll can cause noticeable delays
     // when scrolling a page with a fixed background image. As an optimization, assuming there are
     // no fixed positoned elements on the page, we can acclerate scrolling (via blitting) if we
@@ skipping 4480 matching lines @@
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const
 {
     return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this) : nullptr;
 }
 
 } // namespace blink