views: Forward declare "class View;" in layout_manager.h

views/layout/box_layout.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 VIEWS_LAYOUT_BOX_LAYOUT_H_
 #define VIEWS_LAYOUT_BOX_LAYOUT_H_
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/compiler_specific.h"
 #include "views/layout/layout_manager.h"
 
+namespace gfx {
+class Size;
+}
+
 namespace views {
 
+class View;
+
 // A Layout manager that arranges child views vertically or horizontally in a
 // side-by-side fashion with spacing around and between the child views. The
 // child views are always sized according to their preferred size. If the
 // host's bounds provide insufficient space, child views will be clamped.
 // Excess space will not be distributed.
 class BoxLayout : public LayoutManager {
  public:
   enum Orientation {
     kHorizontal,
     kVertical,
   };
 
   // Use |inside_border_horizontal_spacing| and
   // |inside_border_vertical_spacing| to add additional space between the child
   // view area and the host view border. |between_child_spacing| controls the
   // space in between child views.
   BoxLayout(Orientation orientation,
             int inside_border_horizontal_spacing,
             int inside_border_vertical_spacing,
             int between_child_spacing);
-  virtual ~BoxLayout() {}
+  virtual ~BoxLayout();
 
   // Overridden from views::LayoutManager:
-  virtual void Layout(View* host);
-  virtual gfx::Size GetPreferredSize(View* host);
+  virtual void Layout(View* host) OVERRIDE;
+  virtual gfx::Size GetPreferredSize(View* host) OVERRIDE;
 
  private:
   const Orientation orientation_;
 
   // Spacing between child views and host view border.
   const int inside_border_horizontal_spacing_;
   const int inside_border_vertical_spacing_;
 
   // Spacing to put in between child views.
   const int between_child_spacing_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BoxLayout);
 };
 
 } // namespace views
 
 #endif // VIEWS_LAYOUT_BOX_LAYOUT_H_