exo: Use aura::Windows instead of views::Views as exo::Surfaces.

components/exo/shell_surface.h

 // Copyright 2015 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 COMPONENTS_EXO_SHELL_SURFACE_H_
 #define COMPONENTS_EXO_SHELL_SURFACE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
 }
 
 namespace exo {
 class Surface;
 
 // This class provides functions for treating a surfaces like toplevel,
 // fullscreen or popup widgets, move, resize or maximize them, associate
 // metadata like title and class, etc.
 class ShellSurface : public SurfaceDelegate,
                      public SurfaceObserver,
-                     public views::WidgetDelegate {
+                     public views::WidgetDelegate,
+                     public views::View {
  public:
   explicit ShellSurface(Surface* surface);
   ~ShellSurface() override;
 
   // Show surface as a toplevel window.
   void SetToplevel();
 
   // Maximize or show surface as a maximized window.
   void SetMaximized();
 
@@ skipping 17 matching lines @@
   void OnSurfaceDestroying(Surface* surface) override;
 
   // Overridden from views::WidgetDelegate:
   base::string16 GetWindowTitle() const override;
   views::Widget* GetWidget() override;
   const views::Widget* GetWidget() const override;
   views::View* GetContentsView() override;
   views::NonClientFrameView* CreateNonClientFrameView(
       views::Widget* widget) override;
 
+  // Overridden from views::View:
+  gfx::Size GetPreferredSize() const override;
+
  private:
   scoped_ptr<views::Widget> widget_;
   Surface* surface_;
   base::string16 title_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellSurface);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_SHELL_SURFACE_H_