Clean up code and logic related to platform accessibility node destruction.

ui/accessibility/platform/ax_platform_node_base.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 UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_BASE_H_
 #define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_BASE_H_
 
 #include "base/macros.h"
 #include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/platform/ax_platform_node.h"
@@ skipping 55 matching lines @@
 
  protected:
   AXPlatformNodeBase();
   ~AXPlatformNodeBase() override;
 
   // Cast a gfx::NativeViewAccessible to an AXPlatformNodeBase if it is one,
   // or return NULL if it's not an instance of this class.
   static AXPlatformNodeBase* FromNativeViewAccessible(
       gfx::NativeViewAccessible accessible);
 
-
+  virtual void Dispose();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AXPlatformNodeBase);
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_BASE_H_