Use ScopedTaskEnvironment instead of MessageLoopForUI in ios tests.

ios/chrome/browser/ui/settings/translate_collection_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/settings/translate_collection_view_controller.h"
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_member.h"
 #include "components/prefs/pref_service.h"
 #include "components/strings/grit/components_locale_settings.h"
 #include "components/sync_preferences/pref_service_mock_factory.h"
 #include "components/translate/core/browser/translate_pref_names.h"
 #include "components/translate/core/browser/translate_prefs.h"
 #include "ios/chrome/browser/pref_names.h"
 #import "ios/chrome/browser/translate/chrome_ios_translate_client.h"
@@ skipping 13 matching lines @@
 
 namespace {
 
 const char kBlacklistedSite[] = "http://blacklistedsite.com";
 const char kLanguage1[] = "klingon";
 const char kLanguage2[] = "pirate";
 
 class TranslateCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
+  TranslateCollectionViewControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
   }
 
   CollectionViewController* InstantiateController() override {
     return [[TranslateCollectionViewController alloc]
         initWithPrefs:pref_service_.get()];
   }
 
   std::unique_ptr<PrefService> CreateLocalState() {
     scoped_refptr<PrefRegistrySyncable> registry = new PrefRegistrySyncable();
     registry->RegisterBooleanPref(prefs::kEnableTranslate, false,
                                   PrefRegistrySyncable::SYNCABLE_PREF);
     translate::TranslatePrefs::RegisterProfilePrefs(registry.get());
     registry->RegisterStringPref(
         prefs::kAcceptLanguages,
         l10n_util::GetStringUTF8(IDS_ACCEPT_LANGUAGES));
     base::FilePath path("TranslateCollectionViewControllerTest.pref");
     sync_preferences::PrefServiceMockFactory factory;
     factory.SetUserPrefsFile(path, base::ThreadTaskRunnerHandle::Get().get());
     return factory.Create(registry.get());
   }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   std::unique_ptr<PrefService> pref_service_;
 };
 
 TEST_F(TranslateCollectionViewControllerTest, TestModelTranslateOff) {
   CreateController();
   CheckController();
   EXPECT_EQ(2, NumberOfSections());
   EXPECT_EQ(2, NumberOfItemsInSection(0));
   CheckSwitchCellStateAndTitleWithId(NO, IDS_IOS_TRANSLATE_SETTING, 0, 0);
   CheckTextCellTitleWithId(IDS_IOS_TRANSLATE_SETTING_RESET, 0, 1);
@@ skipping 29 matching lines @@
   [controller collectionView:[controller collectionView]
       didSelectItemAtIndexPath:[NSIndexPath indexPathForItem:1 inSection:0]];
   // Check that preferences are gone.
   EXPECT_FALSE(translate_prefs->IsSiteBlacklisted(kBlacklistedSite));
   EXPECT_FALSE(translate_prefs->IsBlockedLanguage(kLanguage1));
   EXPECT_FALSE(
       translate_prefs->IsLanguagePairWhitelisted(kLanguage1, kLanguage2));
 }
 
 }  // namespace