Reland of [ObjC ARC] Converts ios/chrome/browser/ui/contextual_search:contextual_search to ARC.

ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_CONTEXTUAL_SEARCH_TOUCH_TO_SEARCH_PERMISSIONS_MEDIATOR_H_
 #define IOS_CHROME_BROWSER_UI_CONTEXTUAL_SEARCH_TOUCH_TO_SEARCH_PERMISSIONS_MEDIATOR_H_
 
 #import <Foundation/Foundation.h>
 
 #import "url/gurl.h"
@@ skipping 40 matching lines @@
     NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 // Current preference state. Assigning to this property will update the internal
 // representation backing this state.
 @property(nonatomic, assign)
     TouchToSearch::TouchToSearchPreferenceState preferenceState;
 
 // Current audience object.
-@property(nonatomic, assign)
+@property(nonatomic, weak)
     NSObject<TouchToSearchPermissionsChangeAudience>* audience;
 
 // YES if, given the current permissions state, touch-to-search can be enabled.
 - (BOOL)canEnable;
 
 // YES if, given the current permissions state, surrounding text in |URL| may be
 // extracted.
 - (BOOL)canExtractTapContextForURL:(const GURL&)url;
 
 // YES if it is permitted to send page URLs to the contextual search service.
 - (BOOL)canSendPageURLs;
 
 // YES if search results pages can be preloaded.
 - (BOOL)canPreloadSearchResults;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTEXTUAL_SEARCH_TOUCH_TO_SEARCH_PERMISSIONS_MEDIATOR_H_