Ensure that positioned objects' list is always in parent first order

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. 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
@@ skipping 301 matching lines @@
             while (cb && (cb->style()->position() == StaticPosition || (cb->isInline() && !cb->isReplaced())) && !cb->isRenderView()) {
                 if (cb->style()->position() == RelativePosition && cb->isInline() && !cb->isReplaced()) {
                     cb = cb->containingBlock();
                     break;
                 }
                 cb = cb->parent();
             }
 
             if (cb->isRenderBlock())
                 toRenderBlock(cb)->removePositionedObjects(this, NewContainingBlock);
+        } else if (oldStyle->position() != newStyle.position()) {
+            for (RenderObject* curr = parent(); curr; curr = curr->parent()) {
+                if (curr->isRenderBlock())
+                    toRenderBlock(curr)->removePositionedObjects(this, NewContainingBlock);
+            }
         }
     }
 
     RenderBox::styleWillChange(diff, newStyle);
 }
 
 static bool borderOrPaddingLogicalWidthChanged(const RenderStyle* oldStyle, const RenderStyle* newStyle)
 {
     if (newStyle->isHorizontalWritingMode())
         return oldStyle->borderLeftWidth() != newStyle->borderLeftWidth()
@@ skipping 1600 matching lines @@
     if (!descendantsMap) {
         descendantsMap = new TrackedDescendantsMap;
         containerMap = new TrackedContainerMap;
     }
 
     TrackedRendererListHashSet* descendantSet = descendantsMap->get(this);
     if (!descendantSet) {
         descendantSet = new TrackedRendererListHashSet;
         descendantsMap->set(this, adoptPtr(descendantSet));
     }
-    bool added = descendantSet->add(descendant).isNewEntry;
-    if (!added) {
+
+    if (descendantSet->contains(descendant)) {
         ASSERT(containerMap->get(descendant));
         ASSERT(containerMap->get(descendant)->contains(this));
         return;
     }
+    descendantSet->add(descendant);
 
     HashSet<RenderBlock*>* containerSet = containerMap->get(descendant);
     if (!containerSet) {
         containerSet = new HashSet<RenderBlock*>;
         containerMap->set(descendant, adoptPtr(containerSet));
     }
     ASSERT(!containerSet->contains(this));
     containerSet->add(this);
 }
 
@@ skipping 1983 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace blink