Use ScopedTaskEnvironment instead of MessageLoopForUI in ios tests.

ios/chrome/browser/ui/settings/time_range_selector_collection_view_controller_unittest.mm

 // Copyright 2016 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/time_range_selector_collection_view_controller.h"
 
 #include "base/files/file_path.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/browsing_data/core/pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/sync_preferences/pref_service_mock_factory.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_text_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller_test.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "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
 
 @interface TimeRangeSelectorCollectionViewController (ExposedForTesting)
 - (void)updatePrefValue:(int)prefValue;
 @end
 
 namespace {
 
 const NSInteger kNumberOfItems = 5;
 
 class TimeRangeSelectorCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
+  TimeRangeSelectorCollectionViewControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
     delegate_ = [OCMockObject
         mockForProtocol:@protocol(
                             TimeRangeSelectorCollectionViewControllerDelegate)];
     CreateController();
   }
 
   CollectionViewController* InstantiateController() override {
@@ skipping 12 matching lines @@
     return factory.Create(registry.get());
   }
 
   // Verifies that the cell at |item| in |section| has the given |accessory|
   // type.
   void CheckTextItemAccessoryType(int accessory_type, int section, int item) {
     CollectionViewTextItem* cell = GetCollectionViewItem(section, item);
     EXPECT_EQ(accessory_type, cell.accessoryType);
   }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   std::unique_ptr<PrefService> pref_service_;
   id delegate_;
   TimeRangeSelectorCollectionViewController* time_range_selector_controller_;
 };
 
 TEST_F(TimeRangeSelectorCollectionViewControllerTest, TestModel) {
   CheckController();
   EXPECT_EQ(1, NumberOfSections());
 
   // No section header + 5 rows
@@ skipping 49 matching lines @@
     [time_range_selector_controller_ collectionView:collectionView
                            didSelectItemAtIndexPath:indexPath];
     EXPECT_EQ(
         pref_service_->GetInteger(browsing_data::prefs::kDeleteTimePeriod),
         checkedItem);
     EXPECT_OCMOCK_VERIFY(delegate_);
   }
 }
 
 }  // namespace