*** FOR PROTOTYPE PURPOSES ONLY! NOT INTENDED FOR COMMIT! ***

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index c0de169ae7ec0f9b7a3895708c42166f0a5e6e09..cca2dc64ab6e00c2684f9fdc225c4c23572a7f6b 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -175,6 +175,10 @@ public:
     virtual RenderObjectChildList* virtualChildren() { return 0; }
     virtual const RenderObjectChildList* virtualChildren() const { return 0; }
 
+    // Introduce a non-recursive traversal algorithm for layout
+    enum Order { Pre, Post };
+    RenderObject* nextForLayout(Order& order, const RenderObject* stayWithin, bool skippingChildren) const;
+
     RenderObject* nextInPreOrder() const;
     RenderObject* nextInPreOrder(const RenderObject* stayWithin) const;
     RenderObject* nextInPreOrderAfterChildren() const;
@@ -665,6 +669,15 @@ public:
     // Subclasses must reimplement this method to compute the size and position
     // of this object and all its descendants.
     virtual void layout() = 0;
+
+    // These are hooks into the non-recursive layout variation.  Each subclass
+    // would override these methods and implement non-recursive layout.
+    virtual bool isNonRecursiveLayout() const { return false; }
+    // We have pre/post layout methods in order to facilitate work to be done
+    // before children are visited and after.
+    virtual void preLayout() { ASSERT_NOT_REACHED(); }
+    virtual void postLayout() { ASSERT_NOT_REACHED(); }
+
     virtual bool updateImageLoadingPriorities() { return false; }
     void setHasPendingResourceUpdate(bool hasPendingResourceUpdate) { m_bitfields.setHasPendingResourceUpdate(hasPendingResourceUpdate); }
     bool hasPendingResourceUpdate() const { return m_bitfields.hasPendingResourceUpdate(); }