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

ios/chrome/browser/ui/bookmarks/bookmark_promo_controller.h

 // Copyright 2014 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_CHROME_BROWSER_UI_BOOKMARKS_BOOKMARK_PROMO_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_BOOKMARKS_BOOKMARK_PROMO_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 namespace ios {
 class ChromeBrowserState;
 }  // namespace ios
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }  // namespace user_prefs
 
 @protocol BookmarkPromoControllerDelegate
 
 // Controls the state of the promo.
 - (void)promoStateChanged:(BOOL)promoEnabled;
 
 @end
 
 // This controller manages the display of the promo cell through its delegate
 // and handles displaying the sign-in view controller.
 @interface BookmarkPromoController : NSObject
 
-@property(nonatomic, assign) id<BookmarkPromoControllerDelegate> delegate;
+@property(nonatomic, weak) id<BookmarkPromoControllerDelegate> delegate;
 
 // Holds the current state of the promo. When the promo state change, it will
 // call the promoStateChanged: selector on the delegate.
 @property(nonatomic, assign) BOOL promoState;
 
 // Registers the feature preferences.
 + (void)registerBrowserStatePrefs:(user_prefs::PrefRegistrySyncable*)registry;
 
 - (instancetype)initWithBrowserState:(ios::ChromeBrowserState*)browserState
                             delegate:
                                 (id<BookmarkPromoControllerDelegate>)delegate;
 
 // Presents the sign-in UI.
 - (void)showSignIn;
 
 // Hides the promo cell. It won't be presented again on this profile.
 - (void)hidePromoCell;
 
 // Updates the promo state based on the sign-in state of the user.
 - (void)updatePromoState;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_BOOKMARKS_BOOKMARK_PROMO_CONTROLLER_H_