Introduce centered view and bottom view for home card.

athena/home/minimized_home.h

 // Copyright 2014 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 ATHENA_HOME_MINIMIZED_HOME_H_
 #define ATHENA_HOME_MINIMIZED_HOME_H_
 
-namespace aura {
-class Window;
-}
-
 namespace views {
-class Widget;
+class View;
 }
 
 namespace athena {
 
 class MinimizedHomeDragDelegate {
  public:
   virtual ~MinimizedHomeDragDelegate() {}
 
   virtual void OnDragUpCompleted() = 0;
 };
 
-// Note that |delegate| is guaranteed to be alive as long as the returned widget
+// Note that |delegate| is guaranteed to be alive as long as the returned view
 // is alive.
-views::Widget* CreateMinimizedHome(aura::Window* container,
-                                   MinimizedHomeDragDelegate* delegate);
+views::View* CreateMinimizedHome(MinimizedHomeDragDelegate* delegate);
 
 }  // namespace athena
 
 #endif  // ATHENA_HOME_MINIMIZED_HOME_H_