[ObjC ARC] Converts ios/chrome/browser/ui/history:history to ARC.

ios/chrome/browser/ui/history/history_service_facade.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.
 
 #import "ios/chrome/browser/ui/history/history_service_facade.h"
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 19 matching lines @@
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/history/history_service_factory.h"
 #include "ios/chrome/browser/history/history_utils.h"
 #include "ios/chrome/browser/history/web_history_service_factory.h"
 #include "ios/chrome/browser/pref_names.h"
 #include "ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.h"
 #include "ios/chrome/browser/ui/history/history_entry.h"
 #include "ios/chrome/browser/ui/history/history_service_facade_delegate.h"
 #include "ios/chrome/browser/ui/history/history_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // The amount of time to wait for a response from the WebHistoryService.
 static const int kWebHistoryTimeoutSeconds = 3;
 
 namespace {
 
 // Buckets for UMA histograms.
 enum WebHistoryQueryBuckets {
   WEB_HISTORY_QUERY_FAILED = 0,
   WEB_HISTORY_QUERY_SUCCEEDED,
   WEB_HISTORY_QUERY_TIMED_OUT,
@@ skipping 71 matching lines @@
   history::HistoryService* history_service =
       ios::HistoryServiceFactory::GetForBrowserState(
           browser_state, ServiceAccessType::EXPLICIT_ACCESS);
   if (history_service)
     history_service_observer_.Add(history_service);
 }
 
 HistoryServiceFacade::~HistoryServiceFacade() {
   query_task_tracker_.TryCancelAll();
   web_history_request_.reset();
-  delegate_.reset();
+  delegate_ = nil;
 }
 
 void HistoryServiceFacade::QueryHistory(const base::string16& search_text,
                                         const history::QueryOptions& options) {
   // Anything in-flight is invalid.
   query_task_tracker_.TryCancelAll();
   web_history_request_.reset();
 
   // Reset results.
   query_results_.clear();
@@ skipping 314 matching lines @@
     const history::URLRows& deleted_rows,
     const std::set<GURL>& favicon_urls) {
   if (all_history || DeletionsDiffer(deleted_rows, urls_to_be_deleted_)) {
     if ([delegate_
             respondsToSelector:
                 @selector(historyServiceFacadeDidObserveHistoryDeletion:)]) {
       [delegate_ historyServiceFacadeDidObserveHistoryDeletion:this];
     }
   }
 }