Switch SupportsUserData uses to use unique_ptr.

ios/web/web_state/ui/wk_back_forward_list_item_holder.mm

 // 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.
 
 #import "ios/web/web_state/ui/wk_back_forward_list_item_holder.h"
 
+#include "base/memory/ptr_util.h"
 #import "ios/web/public/navigation_item.h"
 
 namespace web {
 
 namespace {
 // Private key used for safe conversion of base::SupportsUserData to
 // web::WKBackForwardListItemHolder in
 // web::WKBackForwardListItemHolder::FromNavigationItem.
 const char kBackForwardListItemIdentifierKey[] =
     "BackForwardListItemIdentifierKey";
 }
 
 WKBackForwardListItemHolder::WKBackForwardListItemHolder()
     : navigation_type_(WKNavigationTypeOther) {}
 
 WKBackForwardListItemHolder::~WKBackForwardListItemHolder() {}
 
 // static
 WKBackForwardListItemHolder* WKBackForwardListItemHolder::FromNavigationItem(
     web::NavigationItem* item) {
   DCHECK(item);
   base::SupportsUserData::Data* user_data =
       item->GetUserData(kBackForwardListItemIdentifierKey);
   if (!user_data) {
     user_data = new WKBackForwardListItemHolder();
-    item->SetUserData(kBackForwardListItemIdentifierKey, user_data);
+    item->SetUserData(kBackForwardListItemIdentifierKey,
+                      base::WrapUnique(user_data));
   }
   return static_cast<WKBackForwardListItemHolder*>(user_data);
 }
 
 }  // namespace web