Switch SupportsUserData uses to use unique_ptr.

ios/web/web_state/ui/wk_back_forward_list_item_holder.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 IOS_WEB_WEB_STATE_UI_WK_BACK_FORWARD_LIST_ITEM_HOLDER_H_
 #define IOS_WEB_WEB_STATE_UI_WK_BACK_FORWARD_LIST_ITEM_HOLDER_H_
 
 #import <WebKit/WebKit.h>
 
 #import "base/ios/weak_nsobject.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "base/supports_user_data.h"
 
 namespace web {
 
 class NavigationItem;
 
 // This class is a wrapper for information needed to implement native
 // WKWebView navigation. WKBackForwardListItemHolder is attached to
 // NavigationItem via the SupportsUserData interface and holds the corresponding
 // WKBackForwardListItem, as well as any state that is inaccessible later and
 // thus needs to be preserved (e.g., WKNavigationType, MIME type).
 class WKBackForwardListItemHolder : public base::SupportsUserData::Data {
  public:
+  ~WKBackForwardListItemHolder() override;
+
   // Returns the WKBackForwardListItemHolder for the NavigationItem |item|.
   // Lazily attaches one if it does not exist. |item| cannot be null.
   static web::WKBackForwardListItemHolder* FromNavigationItem(
       NavigationItem* item);
 
   // Accessors for |item_|. Use these to get/set the association between a
   // NavigationItem and a WKBackForwardListItem. Note that
   // |back_forward_list_item| may return nil (f.e. when the
   // parent WKBackForwardList is deallocated).
   WKBackForwardListItem* back_forward_list_item() const { return item_; }
@@ skipping 13 matching lines @@
   }
 
   // Gets/sets the MIME type of the page corresponding to this item.
   NSString* mime_type() const { return mime_type_.get(); }
   void set_mime_type(NSString* mime_type) {
     mime_type_.reset([mime_type copy]);
   }
 
  private:
   WKBackForwardListItemHolder();
-  ~WKBackForwardListItemHolder() override;
 
   // Weak pointer to a WKBackForwardListItem. Becomes nil if the parent
   // WKBackForwardList is deallocated.
   base::WeakNSObject<WKBackForwardListItem> item_;
 
   // The navigation type for the associated NavigationItem.
   WKNavigationType navigation_type_;
 
   // HTTP request method.
   base::scoped_nsobject<NSString> http_method_;
 
   // The MIME type of the page content.
   base::scoped_nsobject<NSString> mime_type_;
 
   DISALLOW_COPY_AND_ASSIGN(WKBackForwardListItemHolder);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_WEB_STATE_UI_WK_BACK_FORWARD_LIST_ITEM_HOLDER_H_