Adds a ServerViewObserver interface

services/view_manager/server_view_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 SERVICES_VIEW_MANAGER_SERVER_VIEW_DELEGATE_H_
 #define SERVICES_VIEW_MANAGER_SERVER_VIEW_DELEGATE_H_
 
 #include "mojo/services/view_manager/public/interfaces/view_manager_constants.mojom.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace mojo {
 class ViewportMetrics;
 }
 
 namespace view_manager {
 
 class ServerView;
 
+// ServerViewDelegate is notified at key points in the lifetime of a
+// ServerView. Some of the functions are similar to that of
+// ServerViewObserver. For example, ServerViewDelegate::PrepareToDestroyView()
+// and ServerViewObserver::OnWillDestroyView(). The key difference between
+// the two are the ServerViewDelegate ones are always notified first, and
+// ServerViewDelegate gets non-const arguments.
 class ServerViewDelegate {
  public:
   // Invoked when a view is about to be destroyed; before any of the children
   // have been removed and before the view has been removed from its parent.
-  virtual void OnWillDestroyView(ServerView* view) = 0;
+  virtual void PrepareToDestroyView(ServerView* view) = 0;
 
-  // Invoked at the end of the View's destructor (after it has been removed from
-  // the hierarchy).
-  virtual void OnViewDestroyed(const ServerView* view) = 0;
+  virtual void PrepareToChangeViewHierarchy(ServerView* view,
+                                            ServerView* new_parent,
+                                            ServerView* old_parent) = 0;
 
-  virtual void OnWillChangeViewHierarchy(ServerView* view,
-                                         ServerView* new_parent,
-                                         ServerView* old_parent) = 0;
-
-  virtual void OnViewHierarchyChanged(const ServerView* view,
-                                      const ServerView* new_parent,
-                                      const ServerView* old_parent) = 0;
-
-  virtual void OnViewBoundsChanged(const ServerView* view,
-                                   const gfx::Rect& old_bounds,
-                                   const gfx::Rect& new_bounds) = 0;
-
-  virtual void OnViewSurfaceIdChanged(const ServerView* view) = 0;
-
-  virtual void OnViewReordered(const ServerView* view,
-                               const ServerView* relative,
-                               mojo::OrderDirection direction) = 0;
-
-  virtual void OnWillChangeViewVisibility(ServerView* view) = 0;
-
-  virtual void OnViewSharedPropertyChanged(
-      const ServerView* view,
-      const std::string& name,
-      const std::vector<uint8_t>* new_data) = 0;
+  virtual void PrepareToChangeViewVisibility(ServerView* view) = 0;
 
   virtual void OnScheduleViewPaint(const ServerView* view) = 0;
 
  protected:
   virtual ~ServerViewDelegate() {}
 };
 
 }  // namespace view_manager
 
 #endif  // SERVICES_VIEW_MANAGER_SERVER_VIEW_DELEGATE_H_