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

ios/chrome/browser/ui/chrome_web_view_factory_unittest.mm

 // Copyright 2012 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/chrome_web_view_factory.h"
 
-#include "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "ios/chrome/browser/browser_state/test_chrome_browser_state_isolated_context.h"
 #import "ios/chrome/browser/web/chrome_web_client.h"
 #include "ios/web/net/request_group_util.h"
 #include "ios/web/net/request_tracker_impl.h"
 #include "ios/web/public/test/scoped_testing_web_client.h"
 #include "ios/web/public/test/test_web_thread.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"
 #import "third_party/ocmock/gtest_support.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using web::RequestTrackerImpl;
 
 namespace {
 
 class ChromeWebViewFactoryTest : public PlatformTest {
  public:
   ChromeWebViewFactoryTest()
       : ui_thread_(web::WebThread::UI, &message_loop_),
         io_thread_(web::WebThread::IO, &message_loop_),
         web_client_(base::MakeUnique<ChromeWebClient>()) {}
 
  protected:
   base::MessageLoop message_loop_;
   web::TestWebThread ui_thread_;
   web::TestWebThread io_thread_;
   web::ScopedTestingWebClient web_client_;
   TestChromeBrowserStateWithIsolatedContext chrome_browser_state_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ChromeWebViewFactoryTest);
 };
 
 TEST_F(ChromeWebViewFactoryTest, TestTrackerForExternal) {
   [ChromeWebViewFactory setBrowserStateToUseForExternal:&chrome_browser_state_];
-  base::scoped_nsobject<UIWebView> webView([ChromeWebViewFactory
-      newExternalWebView:chrome_browser_state_.SharingService()]);
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-variable"
+  UIWebView* webView = [ChromeWebViewFactory
+      newExternalWebView:chrome_browser_state_.SharingService()];
+#pragma clang diagnostic pop
   // Check that the tracker is registered
   RequestTrackerImpl* tracker = RequestTrackerImpl::GetTrackerForRequestGroupID(
       ChromeWebView::kExternalRequestGroupID);
   EXPECT_TRUE(tracker) << "Tracker not registered.";
   // External should use the request context for the sharing service, and not
   // the main one.
   net::URLRequestContextGetter* expected_getter = [ChromeWebViewFactory
       requestContextForExternalService:chrome_browser_state_.SharingService()];
   EXPECT_EQ(expected_getter->GetURLRequestContext(),
             tracker->GetRequestContext());
   EXPECT_FALSE(chrome_browser_state_.MainContextCalled());
   // Unregister the tracker.
   [ChromeWebViewFactory externalSessionFinished];
   base::RunLoop().RunUntilIdle();
   EXPECT_FALSE(RequestTrackerImpl::GetTrackerForRequestGroupID(
       ChromeWebView::kExternalRequestGroupID));
   [ChromeWebViewFactory setBrowserStateToUseForExternal:nullptr];
 }
 
 }  // namespace