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

ios/chrome/browser/ui/authentication/signed_in_accounts_view_controller_unittest.mm

 // Copyright 2015 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/ui/authentication/signed_in_accounts_view_controller.h"
 
 #include <memory>
 
 #include "base/strings/sys_string_conversions.h"
 #include "ios/chrome/browser/browser_state/test_chrome_browser_state.h"
 #include "ios/chrome/browser/signin/authentication_service_factory.h"
 #import "ios/chrome/browser/signin/authentication_service_fake.h"
 #include "ios/chrome/test/block_cleanup_test.h"
 #include "ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.h"
 #include "ios/web/public/test/test_web_thread_bundle.h"
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 class SignedInAccountsViewControllerTest : public BlockCleanupTest {
  public:
   void SetUp() override {
     BlockCleanupTest::SetUp();
 
     TestChromeBrowserState::Builder builder;
     builder.AddTestingFactory(
         AuthenticationServiceFactory::GetInstance(),
         AuthenticationServiceFake::CreateAuthenticationService);
     browser_state_ = builder.Build();
@@ skipping 24 matching lines @@
 }
 
 // Tests that the signed in accounts view should be presented when the accounts
 // have changed.
 TEST_F(SignedInAccountsViewControllerTest,
        ShouldBePresentedForBrowserStateNecessary) {
   auth_service_->SetHaveAccountsChanged(true);
   EXPECT_TRUE([SignedInAccountsViewController
       shouldBePresentedForBrowserState:browser_state_.get()]);
 }