Begin getting rid of the recursion in the various RenderObject methods

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index d6c298a73982a99d637007027bab4d7da285f2b1..aeca479f3b763ff231f279de71f300f25e7669e5 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -286,14 +286,12 @@ bool RenderObject::isLegend() const
 
 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);
     }
 }