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

Source/core/rendering/RenderLayerStackingNode.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 285 matching lines @@
         isStacking = isStackingContainer();
         isNormalFlow = isNormalFlowOnly();
         break;
     case OnlyStackingContextsCanBeStackingContainers:
         isStacking = isStackingContext();
         isNormalFlow = shouldBeNormalFlowOnlyIgnoringCompositedScrolling();
         break;
     }
 
     // Overflow layers are just painted by their enclosing layers, so they don't get put in zorder lists.
-    if (!isNormalFlow && !layer()->isOutOfFlowRenderFlowThread()) {
+    if (!isNormalFlow) {
         // Determine which buffer the child should be in.
         OwnPtr<Vector<RenderLayerStackingNode*> >& buffer = (zIndex() >= 0) ? posBuffer : negBuffer;
 
         // Create the buffer if it doesn't exist yet.
         if (!buffer)
             buffer = adoptPtr(new Vector<RenderLayerStackingNode*>);
 
         // Append ourselves at the end of the appropriate buffer.
         buffer->append(this);
     }
@@ skipping 102 matching lines @@
         || renderer()->isCanvas()
         || renderer()->isVideo()
         || renderer()->isEmbeddedObject()
         || renderer()->isRenderIFrame()
         || (renderer()->style()->specifiesColumns() && !layer()->isRootLayer());
     const bool preventsElementFromBeingNormalFlow = renderer()->isPositioned()
         || renderer()->hasTransform()
         || renderer()->hasClipPath()
         || renderer()->hasFilter()
         || renderer()->hasBlendMode()
-        || layer()->isTransparent()
-        || renderer()->style()->hasFlowFrom();
+        || layer()->isTransparent();
 
     return couldBeNormalFlow && !preventsElementFromBeingNormalFlow;
 }
 
 void RenderLayerStackingNode::updateIsNormalFlowOnly()
 {
     bool isNormalFlowOnly = shouldBeNormalFlowOnly();
     if (isNormalFlowOnly == this->isNormalFlowOnly())
         return;
 
@@ skipping 210 matching lines @@
         return ancestor->stackingNode();
     return 0;
 }
 
 RenderLayerModelObject* RenderLayerStackingNode::renderer() const
 {
     return m_layer->renderer();
 }
 
 } // namespace WebCore