Switch SupportsUserData uses to use unique_ptr.

ios/chrome/browser/reading_list/reading_list_web_state_observer.mm

 // Copyright 2016 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.
 
 #include "ios/chrome/browser/reading_list/reading_list_web_state_observer.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 29 matching lines @@
       ReadingListModel* reading_list_model) {
     DCHECK(web_state);
     ReadingListWebStateObserverUserDataWrapper* wrapper =
         static_cast<ReadingListWebStateObserverUserDataWrapper*>(
             web_state->GetUserData(kObserverKey));
     if (!wrapper) {
       auto newDataWrapper =
           base::MakeUnique<ReadingListWebStateObserverUserDataWrapper>(
               web_state, reading_list_model);
       wrapper = newDataWrapper.get();
-      web_state->SetUserData(kObserverKey, newDataWrapper.release());
+      web_state->SetUserData(kObserverKey, std::move(newDataWrapper));
     }
     return wrapper;
   }
 
   ReadingListWebStateObserverUserDataWrapper(
       web::WebState* web_state,
       ReadingListModel* reading_list_model)
       : observer_(web_state, reading_list_model) {
     DCHECK(web_state);
   }
@@ skipping 260 matching lines @@
     // on next navigation.
     // Trigger a new navigation on the offline URL.
     web::WebState::OpenURLParams params(url, item->GetReferrer(),
                                         WindowOpenDisposition::CURRENT_TAB,
                                         item->GetTransitionType(), NO);
     web_state()->OpenURL(params);
   }
   reading_list_model_->SetReadStatus(entry->URL(), true);
   UMA_HISTOGRAM_BOOLEAN("ReadingList.OfflineVersionDisplayed", true);
 }