Use ScopedTaskEnvironment instead of MessageLoopForUI in ui tests.

ui/app_list/pagination_model_unittest.cc

 // Copyright (c) 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.
 
 #include "ui/app_list/pagination_model.h"
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/app_list/pagination_model_observer.h"
 
 namespace app_list {
 namespace test {
 
 class TestPaginationModelObserver : public PaginationModelObserver {
  public:
   TestPaginationModelObserver()
       : model_(NULL),
@@ skipping 81 matching lines @@
   // and |transition_end_count_|. -1 means all the pages should be counted.
   int transition_page_;
 
   std::string selected_pages_;
 
   DISALLOW_COPY_AND_ASSIGN(TestPaginationModelObserver);
 };
 
 class PaginationModelTest : public testing::Test {
  public:
-  PaginationModelTest() {}
+  PaginationModelTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
   ~PaginationModelTest() override {}
 
   // testing::Test overrides:
   void SetUp() override {
     pagination_.SetTotalPages(5);
     pagination_.SetTransitionDurations(1, 1);
     observer_.set_model(&pagination_);
     pagination_.AddObserver(&observer_);
   }
   void TearDown() override {
@@ skipping 11 matching lines @@
     observer_.Reset();
     observer_.set_expected_page_selection(expected_selection);
     observer_.set_expected_transition_start(expected_transition_start);
     observer_.set_expected_transition_end(expected_transition_end);
   }
 
   PaginationModel pagination_;
   TestPaginationModelObserver observer_;
 
  private:
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
   DISALLOW_COPY_AND_ASSIGN(PaginationModelTest);
 };
 
 TEST_F(PaginationModelTest, SelectPage) {
   pagination_.SelectPage(2, false /* animate */);
   pagination_.SelectPage(4, false /* animate */);
   pagination_.SelectPage(3, false /* animate */);
   pagination_.SelectPage(1, false /* animate */);
 
@@ skipping 266 matching lines @@
   EXPECT_EQ(1, pagination_.selected_page());
 
   // But if the currently selected_page exceeds the total number of pages,
   // it automatically switches to the last page.
   pagination_.SetTotalPages(1);
   EXPECT_EQ(0, pagination_.selected_page());
 }
 
 }  // namespace test
 }  // namespace app_list