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

ui/accessibility/platform/ax_platform_node_mac.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_AX_PLATFORM_NODE_MAC_H_
 #define UI_ACCESSIBILITY_AX_PLATFORM_NODE_MAC_H_
 
 #import <Foundation/Foundation.h>
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "ui/accessibility/ax_export.h"
 #include "ui/accessibility/platform/ax_platform_node_base.h"
 
 @class AXPlatformNodeCocoa;
 
 namespace ui {
 
 class AXPlatformNodeMac : public AXPlatformNodeBase {
  public:
   AXPlatformNodeMac();
 
   // AXPlatformNode.
-  void Destroy() override;
   gfx::NativeViewAccessible GetNativeViewAccessible() override;
   void NotifyAccessibilityEvent(ui::AXEvent event_type) override;
 
   // AXPlatformNodeBase.
+  void Destroy() override;
   int GetIndexInParent() override;
 
  private:
   ~AXPlatformNodeMac() override;
 
   base::scoped_nsobject<AXPlatformNodeCocoa> native_node_;
 
   DISALLOW_COPY_AND_ASSIGN(AXPlatformNodeMac);
 };
 
 }  // namespace ui
 
 AX_EXPORT
 @interface AXPlatformNodeCocoa : NSObject {
  @private
   ui::AXPlatformNodeBase* node_;  // Weak. Retains us.
 }
 
 + (NSString*)nativeRoleFromAXRole:(ui::AXRole)role;
 + (NSString*)nativeSubroleFromAXRole:(ui::AXRole)role;
 
 - (instancetype)initWithNode:(ui::AXPlatformNodeBase*)node;
 - (void)detach;
 
 @property(nonatomic, readonly) NSRect boundsInScreen;
 
 @end
 
 #endif  // UI_ACCESSIBILITY_AX_PLATFORM_NODE_MAC_H_