First step at synchronizing client model changes with service.

mojo/services/public/cpp/view_manager/view_tree_node.h

Index: mojo/services/public/cpp/view_manager/view_tree_node.h
diff --git a/mojo/services/public/cpp/view_manager/view_tree_node.h b/mojo/services/public/cpp/view_manager/view_tree_node.h
index 42f27e71f3dbd2c5b495161b0019c6009b252367..d187c662c8fdcf5318958ea19d3d133e98a58c76 100644
--- a/mojo/services/public/cpp/view_manager/view_tree_node.h
+++ b/mojo/services/public/cpp/view_manager/view_tree_node.h
@@ -14,16 +14,19 @@ namespace mojo {
 namespace services {
 namespace view_manager {
 
+class ViewManager;
 class ViewTreeNodeObserver;
 
 class ViewTreeNode {
  public:
   typedef std::vector<ViewTreeNode*> Children;
 
-  ViewTreeNode();
+  explicit ViewTreeNode(ViewManager* manager);
+  ViewTreeNode();  // Used for tests.
   ~ViewTreeNode();
 
   // Configuration.
+  uint16_t id() const { return id_; }
   void set_owned_by_parent(bool owned_by_parent) {
     owned_by_parent_ = owned_by_parent;
   }
@@ -45,6 +48,8 @@ class ViewTreeNode {
  private:
   friend class ViewTreeNodePrivate;
 
+  ViewManager* manager_;
+  uint16_t id_;
   bool owned_by_parent_;
   ViewTreeNode* parent_;
   Children children_;