Need a deep layout pass when becoming (un)fragmented.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc.
  *               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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 217 matching lines @@
 }
 
 void LayoutView::layout() {
   if (!document().paginated())
     setPageLogicalHeight(LayoutUnit());
 
   setShouldDoFullPaintInvalidationOnResizeIfNeeded();
 
   if (pageLogicalHeight() && shouldUsePrintingLayout()) {
     m_minPreferredLogicalWidth = m_maxPreferredLogicalWidth = logicalWidth();
-    if (!m_fragmentationContext)
+    if (!m_fragmentationContext) {
       m_fragmentationContext = wrapUnique(new ViewFragmentationContext(*this));
+      m_paginationStateChanged = true;
+    }
   } else if (m_fragmentationContext) {
     m_fragmentationContext.reset();
+    m_paginationStateChanged = true;
   }
 
   SubtreeLayoutScope layoutScope(*this);
 
   LayoutRect oldLayoutOverflowRect = layoutOverflowRect();
 
   // Use calcWidth/Height to get the new width/height, since this will take the
   // full page zoom factor into account.
   bool relayoutChildren =
       !shouldUsePrintingLayout() &&
@@ skipping 810 matching lines @@
   if (block)
     block->adjustChildDebugRect(rect);
 
   rect.setWidth(LayoutUnit(viewWidth(IncludeScrollbars)));
   rect.setHeight(LayoutUnit(viewHeight(IncludeScrollbars)));
 
   return rect;
 }
 
 }  // namespace blink