Add support for mapping node tree on the client.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_MANAGER_H_
 #define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_MANAGER_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/observer_list.h"
+#include "mojo/public/cpp/bindings/callback.h"
+#include "mojo/services/public/cpp/view_manager/view_tree_node.h"
 
 namespace mojo {
 class Shell;
 namespace services {
 namespace view_manager {
 
+class ViewManagerObserver;
 class ViewManagerSynchronizer;
+class ViewTreeNode;
 
 // Approximately encapsulates the View Manager service.
 // Owns a synchronizer that keeps a client model in sync with the service.
 // Owned by the creator.
 //
 // TODO: displays
 class ViewManager {
  public:
   explicit ViewManager(Shell* shell);
   ~ViewManager();
 
+  void BuildNodeTree(const mojo::Callback<void()>& callback);
+
+  ViewTreeNode* tree() { return tree_.get(); }
+
  private:
   friend class ViewManagerPrivate;
 
+  void AddObserver(ViewManagerObserver* observer);
+  void RemoveObserver(ViewManagerObserver* observer);
+
   Shell* shell_;
   scoped_ptr<ViewManagerSynchronizer> synchronizer_;
+  scoped_ptr<ViewTreeNode> tree_;
+
+  ObserverList<ViewManagerObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewManager);
 };
 
 }  // namespace view_manager
 }  // namespace services
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_MANAGER_H_