[ObjC ARC] Converts components/signin/ios/browser:browser to ARC.

components/signin/ios/browser/merge_session_observer_bridge.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 COMPONENTS_SIGNIN_IOS_BROWSER_MERGE_SESSION_OBSERVER_BRIDGE_H_
 #define COMPONENTS_SIGNIN_IOS_BROWSER_MERGE_SESSION_OBSERVER_BRIDGE_H_
 
 #import <Foundation/Foundation.h>
 
 #include <string>
 
+#import "base/ios/weak_nsobject.h"
 #include "base/macros.h"
 #include "components/signin/core/browser/gaia_cookie_manager_service.h"
 
 class GoogleServiceAuthError;
 
 @protocol MergeSessionObserverBridgeDelegate
 
 // Informs the delegate that the merge session operation for |account_id| has
 // finished. If there was an error, it will be described in |error|.
 - (void)onMergeSessionCompleted:(const std::string&)account_id
                           error:(const GoogleServiceAuthError&)error;
 
 @end
 
 // C++ class to monitor merge session status in Objective C type.
 class MergeSessionObserverBridge : public GaiaCookieManagerService::Observer {
  public:
   MergeSessionObserverBridge(id<MergeSessionObserverBridgeDelegate> delegate,
                              GaiaCookieManagerService* cookie_manager_service);
   ~MergeSessionObserverBridge() override;
 
   void OnAddAccountToCookieCompleted(
       const std::string& account_id,
       const GoogleServiceAuthError& error) override;
 
  private:
-  id<MergeSessionObserverBridgeDelegate> delegate_;
+  base::WeakNSProtocol<id<MergeSessionObserverBridgeDelegate>> delegate_;

[stkhapugin, 2017/06/13 12:18:55]

This seems to be included only from the corresponding .mm, so you can try making
this __weak instead. 

[msarda, 2017/06/13 13:15:30]

I do not know that much about ARC transition, so this is probably a newbie
question: Shouldn't this be __weak (or maybe a weak property) instead of
base::WeakNSProtocol?

[marq (ping after 24h), 2017/06/15 09:27:33]

Because it's in a header, it can only be __weak if it's only included in ARC
targets. Otherwise it needs to be a WeakNSProtocol. It looks like we can change
this one, though.

   GaiaCookieManagerService* cookie_manager_service_;
 
   DISALLOW_COPY_AND_ASSIGN(MergeSessionObserverBridge);
 };
 
 #endif  // COMPONENTS_SIGNIN_IOS_BROWSER_MERGE_SESSION_OBSERVER_BRIDGE_H_