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

ios/chrome/browser/signin/authentication_service_unittest.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.
 
 #include <memory>
 
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/browser_sync/profile_sync_service_mock.h"
@@ skipping 28 matching lines @@
 #include "ios/chrome/test/ios_chrome_scoped_testing_chrome_browser_state_manager.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/signin/chrome_identity.h"
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.h"
 #include "ios/web/public/test/test_web_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using testing::_;
 using testing::Invoke;
 using testing::Return;
 
 namespace {
 
 class FakeSigninClient : public SigninClientImpl {
  public:
   explicit FakeSigninClient(ios::ChromeBrowserState* browser_state)
       : SigninClientImpl(browser_state,
@@ skipping 131 matching lines @@
     authentication_service_->OnAccessTokenRefreshFailed(identity, user_info);
   }
 
   void FireIdentityListChanged() {
     authentication_service_->OnIdentityListChanged();
   }
 
   void SetCachedMDMInfo(ChromeIdentity* identity, NSDictionary* user_info) {
     authentication_service_
         ->cached_mdm_infos_[base::SysNSStringToUTF8([identity gaiaID])]
-        .reset([user_info retain]);
+        .reset(user_info);
   }
 
   bool HasCachedMDMInfo(ChromeIdentity* identity) {
     return authentication_service_->cached_mdm_infos_.count(
                base::SysNSStringToUTF8([identity gaiaID])) > 0;
   }
 
   void OnRefreshTokenAvailable(const std::string& account_id) override {
     refresh_token_available_count_++;
   }
@@ skipping 524 matching lines @@
   NSDictionary* user_info = [NSDictionary dictionary];
   SetCachedMDMInfo(identity_, user_info);
 
   EXPECT_CALL(*identity_service_,
               HandleMDMNotification(identity_, user_info, _))
       .WillOnce(Return(true));
 
   EXPECT_TRUE(
       authentication_service_->ShowMDMErrorDialogForIdentity(identity_));
 }