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

ios/chrome/browser/signin/authentication_service.mm

 // Copyright 2013 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/signin/authentication_service.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/auto_reset.h"
 #include "base/location.h"
@@ skipping 19 matching lines @@
 #include "ios/chrome/browser/signin/constants.h"
 #include "ios/chrome/browser/signin/oauth2_token_service_factory.h"
 #include "ios/chrome/browser/signin/signin_manager_factory.h"
 #include "ios/chrome/browser/signin/signin_util.h"
 #include "ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.h"
 #include "ios/chrome/browser/sync/sync_setup_service.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/signin/chrome_identity.h"
 #include "ios/public/provider/chrome/browser/signin/chrome_identity_service.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 // Enum describing the different sync states per login methods.
 enum LoginMethodAndSyncState {
   // Legacy values retained to keep definitions in histograms.xml in sync.
   CLIENT_LOGIN_SYNC_OFF,
   CLIENT_LOGIN_SYNC_ON,
   SHARED_AUTHENTICATION_SYNC_OFF,
   SHARED_AUTHENTICATION_SYNC_ON,
   // NOTE: Add new login methods and sync states only immediately above this
@@ skipping 62 matching lines @@
       SignOut(signin_metrics::ABORT_SIGNIN, nil);
       SetPromptForSignIn(true);
       isSignedIn = false;
     }
   }
   breakpad_helper::SetCurrentlySignedIn(isSignedIn);
 
   OnApplicationEnterForeground();
 
   NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
-  foreground_observer_.reset(
-      [[center addObserverForName:UIApplicationWillEnterForegroundNotification
-                           object:nil
-                            queue:nil
-                       usingBlock:^(NSNotification* notification) {
-                         OnApplicationEnterForeground();
-                       }] retain]);
-  background_observer_.reset(
-      [[center addObserverForName:UIApplicationDidEnterBackgroundNotification
-                           object:nil
-                            queue:nil
-                       usingBlock:^(NSNotification* notification) {
-                         OnApplicationEnterBackground();
-                       }] retain]);
+  foreground_observer_.reset([center
+      addObserverForName:UIApplicationWillEnterForegroundNotification
+                  object:nil
+                   queue:nil
+              usingBlock:^(NSNotification* notification) {
+                OnApplicationEnterForeground();
+              }]);
+  background_observer_.reset([center
+      addObserverForName:UIApplicationDidEnterBackgroundNotification
+                  object:nil
+                   queue:nil
+              usingBlock:^(NSNotification* notification) {
+                OnApplicationEnterBackground();
+              }]);
 
   identity_service_observer_.Add(
       ios::GetChromeBrowserProvider()->GetChromeIdentityService());
 }
 
 void AuthenticationService::Shutdown() {
   NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
   [center removeObserver:foreground_observer_];
   [center removeObserver:background_observer_];
 }
@@ skipping 337 matching lines @@
     if (is_blocked) {
       // If the identiy is blocked, sign out of the account. As only managed
       // account can be blocked, this will clear the associated browsing data.
       if (identity == GetAuthenticatedIdentity()) {
         SignOut(signin_metrics::ABORT_SIGNIN, nil);
       }
     }
   };
   if (identity_service->HandleMDMNotification(identity, user_info, callback)) {
     cached_mdm_infos_[ChromeIdentityToAccountID(browser_state_, identity)]
-        .reset([user_info retain]);
+        .reset(user_info);

[msarda, 2017/06/26 11:44:47]

It is not clear to me if we need to retain here - this is a map of std:string to
scoped_nsobject. Will the scoped_nsobject increase the retain count correctly in
this case?

[stkhapugin, 2017/06/26 13:06:41]

Yes, scoped_nsobject increase the retain count. If you look at
scoped_nsobject.h, it has basically two implementations for reset() - one for
ARC, one for non-ARC - where the ARC one increases retain count internally,
while the non-ARC one expects a previously-retained object. That's because
explicit calls to -retain are not allowed under ARC. :)

     return true;
   }
   return false;
 }
 
 void AuthenticationService::OnAccessTokenRefreshFailed(
     ChromeIdentity* identity,
     NSDictionary* user_info) {
   if (HandleMDMNotification(identity, user_info)) {
     return;
@@ skipping 103 matching lines @@
     // integration is enabled.
     return false;
   }
   std::string hosted_domain =
       ios::SigninManagerFactory::GetForBrowserState(browser_state_)
           ->GetAuthenticatedAccountInfo()
           .hosted_domain;
   return !hosted_domain.empty() &&
          hosted_domain != AccountTrackerService::kNoHostedDomainFound;
 }