It is time.

ui/views/layout/layout_manager.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_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
-#define UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
-
-#include "ui/views/views_export.h"
-
-namespace gfx {
-class Size;
-}
-
-namespace views {
-
-class View;
-
-/////////////////////////////////////////////////////////////////////////////
-//
-// LayoutManager interface
-//
-//   The LayoutManager interface provides methods to handle the sizing of
-//   the children of a View according to implementation-specific heuristics.
-//
-/////////////////////////////////////////////////////////////////////////////
-class VIEWS_EXPORT LayoutManager {
- public:
-  virtual ~LayoutManager();
-
-  // Notification that this LayoutManager has been installed on a particular
-  // host.
-  virtual void Installed(View* host);
-
-  // Notification that this LayoutManager has been uninstalled on a particular
-  // host.
-  virtual void Uninstalled(View* host);
-
-  // Lay out the children of |host| according to implementation-specific
-  // heuristics. The graphics used during painting is provided to allow for
-  // string sizing.
-  virtual void Layout(View* host) = 0;
-
-  // Return the preferred size which is the size required to give each
-  // children their respective preferred size.
-  virtual gfx::Size GetPreferredSize(const View* host) const = 0;
-
-  // Returns the preferred height for the specified width. The default
-  // implementation returns the value from GetPreferredSize.
-  virtual int GetPreferredHeightForWidth(const View* host, int width) const;
-
-  // Notification that a view has been added.
-  virtual void ViewAdded(View* host, View* view);
-
-  // Notification that a view has been removed.
-  virtual void ViewRemoved(View* host, View* view);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_