Views a11y: Convert View's NativeViewAccessibility to a unique_ptr.

ui/views/view.h

 // Copyright (c) 2012 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_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 1598 matching lines @@
   // Drag and drop -------------------------------------------------------------
 
   DragController* drag_controller_;
 
   // Input  --------------------------------------------------------------------
 
   std::unique_ptr<ViewTargeter> targeter_;
 
   // Accessibility -------------------------------------------------------------
 
-  // Belongs to this view, but it's reference-counted on some platforms
-  // so we can't use a scoped_ptr. It's dereferenced in the destructor.
-  NativeViewAccessibility* native_view_accessibility_;
+  // The accessibility element used to represent this View.
+  std::unique_ptr<NativeViewAccessibility> native_view_accessibility_;
 
   // Observers -------------------------------------------------------------
 
   base::ObserverList<ViewObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_