*** DO NOT LAND *** Attempt to understand Regions complexity

Source/core/rendering/style/RenderStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 162 matching lines @@
         return Reattach;
 
     if (!oldStyle && !newStyle)
         return NoChange;
 
     if (oldStyle->display() != newStyle->display()
         || oldStyle->hasPseudoStyle(FIRST_LETTER) != newStyle->hasPseudoStyle(FIRST_LETTER)
         || oldStyle->columnSpan() != newStyle->columnSpan()
         || oldStyle->specifiesAutoColumns() != newStyle->specifiesAutoColumns()
         || !oldStyle->contentDataEquivalent(newStyle)
-        || oldStyle->hasTextCombine() != newStyle->hasTextCombine()
-        || oldStyle->flowThread() != newStyle->flowThread()
-        || oldStyle->regionThread() != newStyle->regionThread())
+        || oldStyle->hasTextCombine() != newStyle->hasTextCombine())
         return Reattach;
 
     if (*oldStyle == *newStyle)
         return comparePseudoStyles(oldStyle, newStyle);
 
     if (oldStyle->inheritedNotEqual(newStyle)
         || oldStyle->hasExplicitlyInheritedProperties()
         || newStyle->hasExplicitlyInheritedProperties())
         return Inherit;
 
@@ skipping 214 matching lines @@
             || borderRightWidth() != other->borderRightWidth())
             return StyleDifferenceLayout;
     }
 
     if (rareNonInheritedData.get() != other->rareNonInheritedData.get()) {
         if (rareNonInheritedData->m_appearance != other->rareNonInheritedData->m_appearance
             || rareNonInheritedData->marginBeforeCollapse != other->rareNonInheritedData->marginBeforeCollapse
             || rareNonInheritedData->marginAfterCollapse != other->rareNonInheritedData->marginAfterCollapse
             || rareNonInheritedData->lineClamp != other->rareNonInheritedData->lineClamp
             || rareNonInheritedData->textOverflow != other->rareNonInheritedData->textOverflow
-            || rareNonInheritedData->m_regionFragment != other->rareNonInheritedData->m_regionFragment
             || rareNonInheritedData->m_wrapFlow != other->rareNonInheritedData->m_wrapFlow
             || rareNonInheritedData->m_wrapThrough != other->rareNonInheritedData->m_wrapThrough
             || rareNonInheritedData->m_shapeMargin != other->rareNonInheritedData->m_shapeMargin
             || rareNonInheritedData->m_shapePadding != other->rareNonInheritedData->m_shapePadding
             || rareNonInheritedData->m_order != other->rareNonInheritedData->m_order
             || rareNonInheritedData->m_alignContent != other->rareNonInheritedData->m_alignContent
             || rareNonInheritedData->m_alignItems != other->rareNonInheritedData->m_alignItems
             || rareNonInheritedData->m_alignSelf != other->rareNonInheritedData->m_alignSelf
             || rareNonInheritedData->m_justifyContent != other->rareNonInheritedData->m_justifyContent
             || rareNonInheritedData->m_grid.get() != other->rareNonInheritedData->m_grid.get()
@@ skipping 1160 matching lines @@
 }
 
 void RenderStyle::setBorderImageOutset(const BorderImageLengthBox& outset)
 {
     if (surround->border.m_image.outset() == outset)
         return;
     surround.access()->border.m_image.setOutset(outset);
 }
 
 } // namespace WebCore