View synchronization

mojo/services/public/cpp/view_manager/view_tree_node_observer.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_TREE_NODE_OBSERVER_H_
 #define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_TREE_NODE_OBSERVER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 
 namespace mojo {
 namespace services {
 namespace view_manager {
 
+class View;
 class ViewTreeNode;
 
 class ViewTreeNodeObserver {
  public:
   enum DispositionChangePhase {
     DISPOSITION_CHANGING,
     DISPOSITION_CHANGED
   };
 
   struct TreeChangeParams {
     TreeChangeParams();
     ViewTreeNode* target;
     ViewTreeNode* old_parent;
     ViewTreeNode* new_parent;
     ViewTreeNode* receiver;
     DispositionChangePhase phase;
   };
 
   virtual void OnTreeChange(const TreeChangeParams& params) {}
 
   virtual void OnNodeDestroy(ViewTreeNode* node,
                              DispositionChangePhase phase) {}
 
+  virtual void OnNodeActiveViewChange(ViewTreeNode* node,
+                                      View* old_view,
+                                      View* new_view,
+                                      DispositionChangePhase phase) {}
+
  protected:
   virtual ~ViewTreeNodeObserver() {}
 };
 
 }  // namespace view_manager
 }  // namespace services
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_TREE_NODE_OBSERVER_H_