Create a LayerDelegate for recreated layers to draw when their content is invalidated.

ui/wm/core/window_util.h

 // Copyright (c) 2012 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 UI_WM_CORE_WINDOW_UTIL_H_
 #define UI_WM_CORE_WINDOW_UTIL_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "ui/wm/wm_export.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ui {
 class Layer;
+class LayerDelegate;
 class LayerOwner;
 class LayerTreeOwner;
 }
 
 namespace wm {
 
 WM_EXPORT void ActivateWindow(aura::Window* window);
 WM_EXPORT void DeactivateWindow(aura::Window* window);
 WM_EXPORT bool IsActiveWindow(aura::Window* window);
 WM_EXPORT bool CanActivateWindow(aura::Window* window);
 
 // Retrieves the activatable window for |window|. The ActivationClient makes
 // this determination.
 WM_EXPORT aura::Window* GetActivatableWindow(aura::Window* window);
 
 // Retrieves the toplevel window for |window|. The ActivationClient makes this
 // determination.
 WM_EXPORT aura::Window* GetToplevelWindow(aura::Window* window);
 
+// A factory method to create a delegate for recreated layers.
+class WM_EXPORT LayerDelegateFactory {
+ public:
+  virtual ~LayerDelegateFactory() = default;
+
+  virtual ui::LayerDelegate* CreateDelegate(
+      ui::LayerDelegate* original_delegate) = 0;

[sky, 2016/05/19 20:06:49]

Document ownership and expected lifetime.

[oshima, 2016/05/19 23:32:21]

Done.

+};
+
 // Returns the existing Layer for |root| (and all its descendants) and creates
 // a new layer for |root| and all its descendants. This is intended for
 // animations that want to animate between the existing visuals and a new state.
 //
 // As a result of this |root| has freshly created layers, meaning the layers
 // have not yet been painted to.
+//
+// When a non null |delegate_factory| is passed, it will be used to
+// create an delegate for an old layer which had its own delegate.

[sky, 2016/05/19 20:06:49]

nit: 'create an' -> 'create a'

[oshima, 2016/05/19 23:32:21]

Done.

 WM_EXPORT std::unique_ptr<ui::LayerTreeOwner> RecreateLayers(
-    ui::LayerOwner* root);
+    ui::LayerOwner* root,
+    LayerDelegateFactory* delegate_factory);
 
 // Convenience functions that get the TransientWindowManager for the window and
 // redirect appropriately. These are preferable to calling functions on
 // TransientWindowManager as they handle the appropriate NULL checks.
 WM_EXPORT aura::Window* GetTransientParent(aura::Window* window);
 WM_EXPORT const aura::Window* GetTransientParent(
     const aura::Window* window);
 WM_EXPORT const std::vector<aura::Window*>& GetTransientChildren(
     const aura::Window* window);
 WM_EXPORT void AddTransientChild(aura::Window* parent, aura::Window* child);
 WM_EXPORT void RemoveTransientChild(aura::Window* parent, aura::Window* child);
 
 // Returns true if |window| has |ancestor| as a transient ancestor. A transient
 // ancestor is found by following the transient parent chain of the window.
 WM_EXPORT bool HasTransientAncestor(const aura::Window* window,
                                     const aura::Window* ancestor);
 
 }  // namespace wm
 
 #endif  // UI_WM_CORE_WINDOW_UTIL_H_