DO NOT COMMIT - fn port to RenderNode, work in progress, does not work

sky/sdk/lib/framework/node.dart

-library node;
-
 class AbstractNode {
 
   // Nodes always have a 'depth' greater than their ancestors'.
   // There's no guarantee regarding depth between siblings. The depth
   // of a node is used to ensure that nodes are processed in depth
   // order. The 'depth' of a child can be more than one greater than
   // the 'depth' of the parent, because the 'depth' values are never
   // decreased: all that matters is that it's greater than the parent.
   // Consider a tree with a root node A, a child B, and a grandchild
   // C. Initially, A will have 'depth' 0, B 'depth' 1, and C 'depth'
@@ skipping 44 matching lines @@
   void dropChild(AbstractNode child) { // only for use by subclasses
     assert(child != null);
     assert(child._parent == this);
     assert(child.attached == attached);
     child._parent = null;
     if (attached)
       child.detach();
   }
 
 }