Add support for mapping node tree on the client.

mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h

Index: mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h
diff --git a/mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h b/mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h
index 33be9f087da1b1fcb4c3c5ad84e7915a5bb7b141..6f60945231003911ba7b4f9d024a03f09ab3ea6b 100644
--- a/mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h
+++ b/mojo/services/public/cpp/view_manager/lib/view_tree_node_private.h
@@ -24,6 +24,16 @@ class ViewTreeNodePrivate {
 
   void ClearParent() { node_->parent_ = NULL; }
 
+  void set_id(TransportNodeId id) { node_->id_ = id; }
+
+  void set_view_manager(ViewManager* manager) {
+    node_->manager_ = manager;
+  }
+
+  void LocalAddChild(ViewTreeNode* child) {
+    node_->LocalAddChild(child);
+  }
+
  private:
   ViewTreeNode* node_;