[ObjC ARC] Converts ios/chrome/browser/device_sharing:device_sharing to ARC.Automatically generat…

ios/chrome/browser/device_sharing/device_sharing_manager.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.
 
 #include "ios/chrome/browser/device_sharing/device_sharing_manager.h"
 
 #include <memory>
 
 #include "base/mac/scoped_nsobject.h"
 #import "components/handoff/handoff_manager.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "components/prefs/pref_service.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/pref_names.h"
 #include "ios/chrome/browser/prefs/pref_observer_bridge.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface DeviceSharingManager ()<PrefObserverDelegate> {
   ios::ChromeBrowserState* _browserState;  // weak
 
   // Bridge to listen to pref changes to the active browser state.
   std::unique_ptr<PrefObserverBridge> _browserStatePrefObserverBridge;
 
   // Registrar for pref change notifications to the active browser state.
   std::unique_ptr<PrefChangeRegistrar> _browserStatePrefChangeRegistrar;
 
   // Responsible for maintaining all state related to the Handoff feature.
@@ skipping 42 matching lines @@
 - (void)updateHandoffManager {
   BOOL handoffEnabled =
       _browserState &&
       _browserState->GetPrefs()->GetBoolean(prefs::kIosHandoffToOtherDevices);
   if (!handoffEnabled) {
     _handoffManager.reset();
     return;
   }
 
   if (!_handoffManager)
-    _handoffManager.reset([[[self class] createHandoffManager] retain]);
+    _handoffManager.reset([[self class] createHandoffManager]);
 }
 
 + (HandoffManager*)createHandoffManager {
-  return [[[HandoffManager alloc] init] autorelease];
+  return [[HandoffManager alloc] init];
 }
 
 #pragma mark - PrefObserverDelegate
 
 - (void)onPreferenceChanged:(const std::string&)preferenceName {
   if (preferenceName == prefs::kIosHandoffToOtherDevices) {
     [self updateHandoffManager];
   }
 }
 
 @end
 
 @implementation DeviceSharingManager (TestingOnly)
 
 - (HandoffManager*)handoffManager {
   return _handoffManager.get();
 }
 
 @end