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

ios/chrome/browser/signin/gaia_auth_fetcher_ios_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.
 
 #include "ios/chrome/browser/signin/gaia_auth_fetcher_ios.h"
 
 #include <memory>
 
-#import "base/mac/scoped_nsobject.h"
 #include "base/run_loop.h"
 #include "google_apis/gaia/gaia_urls.h"
 #include "ios/chrome/browser/signin/gaia_auth_fetcher_ios_private.h"
 #include "ios/web/public/test/fakes/test_browser_state.h"
 #include "ios/web/public/test/test_web_thread_bundle.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 #import "third_party/ocmock/gtest_support.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 class FakeGaiaAuthFetcherIOSBridge : public GaiaAuthFetcherIOSBridge {
  public:
   FakeGaiaAuthFetcherIOSBridge(GaiaAuthFetcherIOS* fetcher,
                                web::BrowserState* browser_state)
       : GaiaAuthFetcherIOSBridge(fetcher, browser_state), mock_web_view_(nil) {}
 
  private:
   WKWebView* BuildWKWebView() override {
     if (!mock_web_view_) {
-      mock_web_view_.reset(
-          [[OCMockObject niceMockForClass:[WKWebView class]] retain]);
+      mock_web_view_ = [OCMockObject niceMockForClass:[WKWebView class]];
     }
     return mock_web_view_;
   }
-  base::scoped_nsobject<id> mock_web_view_;
+  id mock_web_view_;
 };
 
 class MockGaiaConsumer : public GaiaAuthConsumer {
  public:
   MockGaiaConsumer() {}
   ~MockGaiaConsumer() {}
 
   MOCK_METHOD1(OnMergeSessionSuccess, void(const std::string& data));
   MOCK_METHOD1(OnClientLoginFailure, void(const GoogleServiceAuthError& error));
   MOCK_METHOD1(OnLogOutFailure, void(const GoogleServiceAuthError& error));
@@ skipping 134 matching lines @@
   [[GetMockWKWebView() expect] setNavigationDelegate:[OCMArg isNotNil]];
   [static_cast<WKWebView*>([[GetMockWKWebView() expect] andDo:^(NSInvocation*) {
     GetBridge()->URLFetchSuccess("data");
   }]) loadRequest:[OCMArg any]];
 
   gaia_auth_fetcher_->StartMergeSession("uber_token", "");
   web::BrowserState::GetActiveStateManager(&browser_state_)->SetActive(false);
   web::BrowserState::GetActiveStateManager(&browser_state_)->SetActive(true);
   EXPECT_OCMOCK_VERIFY(GetMockWKWebView());
 }