Adds more to viewmanager

mojo/services/view_manager/node_delegate.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_VIEW_MANAGER_NODE_DELEGATE_H_
 #define MOJO_SERVICES_VIEW_MANAGER_NODE_DELEGATE_H_
 
 #include "mojo/services/view_manager/view_manager_export.h"
 
 namespace mojo {
 namespace services {
 namespace view_manager {
 
 struct NodeId;
+struct ViewId;
 
 class MOJO_VIEW_MANAGER_EXPORT NodeDelegate {
  public:
   // Invoked when the hierarchy has changed.
   virtual void OnNodeHierarchyChanged(const NodeId& node,
                                       const NodeId& new_parent,
                                       const NodeId& old_parent) = 0;
 
+  // Invoked when the View associated with a node changes.
+  virtual void OnNodeViewReplaced(const NodeId& node,
+                                  const ViewId& new_view_id,
+                                  const ViewId& old_view_id) = 0;
+
  protected:
   virtual ~NodeDelegate() {}
 };
 
 }  // namespace view_manager
 }  // namespace services
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_VIEW_MANAGER_NODE_DELEGATE_H_