Begin getting rid of the recursion in the various RenderObject methods

Source/core/rendering/RenderObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 268 matching lines @@
     return node() && node()->hasTagName(hrTag);
 }
 
 bool RenderObject::isLegend() const
 {
     return node() && node()->hasTagName(legendTag);
 }
 
 void RenderObject::setFlowThreadStateIncludingDescendants(FlowThreadState state)
 {
-    setFlowThreadState(state);
-
-    for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-        // If the child is a fragmentation context it already updated the descendants flag accordingly.
-        if (child->isRenderFlowThread())
+    for (RenderObject *object = this; object; object = object->nextInPreOrder()) {

[dsinclair, 2014/01/27 20:21:55]

drive by comment: From someone new to the rendering code, the original version
of this is easier to understand what will be affected by the iteration. I'm not
sure I'd have realized (assuming I hadn't seen this patch go in) the
nextInPreOrder() from the current object is the same as looking at all the
descendants.

Is this just to get rid of the recursion, or are there other factors that make
the new version better?

[esprehn, 2014/01/27 20:44:37]

This is not correct, nextInPreOrder() will walk all the way up to the RenderView
since you don't pass a scope.

You need object->nextInPreOrder(this)

+        // If object is a fragmentation context it already updated the descendants flag accordingly.
+        if (object->isRenderFlowThread())
             continue;
-        ASSERT(state != child->flowThreadState());
-        child->setFlowThreadStateIncludingDescendants(state);
+        ASSERT(state != object->flowThreadState());
+        object->setFlowThreadState(state);
     }
 }
 
 bool RenderObject::requiresAnonymousTableWrappers(const RenderObject* newChild) const
 {
     // Check should agree with:
     // CSS 2.1 Tables: 17.2.1 Anonymous table objects
     // http://www.w3.org/TR/CSS21/tables.html#anonymous-boxes
     if (newChild->isRenderTableCol()) {
         const RenderTableCol* newTableColumn = toRenderTableCol(newChild);
@@ skipping 3080 matching lines @@
 {
     if (object1) {
         const WebCore::RenderObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showRenderTreeAndMark(object1, "*", object2, "-", 0);
     }
 }
 
 #endif