aura: Ask the WindowDelegate before a Window is Focus()ed.

ui/aura/window_delegate.h

 // Copyright (c) 2011 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_AURA_WINDOW_DELEGATE_H_
 #define UI_AURA_WINDOW_DELEGATE_H_
 #pragma once
 
 #include "ui/aura/aura_export.h"
 #include "ui/base/events.h"
@@ skipping 34 matching lines @@
   virtual gfx::NativeCursor GetCursor(const gfx::Point& point) = 0;
 
   // Returns the non-client component (see hit_test.h) containing |point|, in
   // window coordinates.
   virtual int GetNonClientComponent(const gfx::Point& point) const = 0;
 
   virtual bool OnMouseEvent(MouseEvent* event) = 0;
 
   virtual ui::TouchStatus OnTouchEvent(TouchEvent* event) = 0;
 
+  // Returns true of the window can be focused.
+  virtual bool CanFocus() = 0;
+
   // Returns true if the window should be activated. |event| is either the mouse
   // event supplied if the activation is the result of a mouse, or the touch
   // event if the activation is the result of a touch, or NULL if activation is
   // attempted for another reason.
   virtual bool ShouldActivate(Event* event) = 0;
 
   // Sent when the window is activated.
   virtual void OnActivated() = 0;
 
   // Sent when the window loses active status.
@@ skipping 18 matching lines @@
   // Called when the visibility of a Window changed.
   virtual void OnWindowVisibilityChanged(bool visible) = 0;
 
  protected:
   virtual ~WindowDelegate() {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_DELEGATE_H_