Use ScopedTaskEnvironment instead of MessageLoopForUI in ash tests.

ash/system/power/power_status_unittest.cc

 // Copyright (c) 2013 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 "ash/system/power/power_status.h"
 
 #include <memory>
 
 #include "ash/resources/vector_icons/vector_icons.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/cros_system_api/dbus/service_constants.h"
 
 using power_manager::PowerSupplyProperties;
 
 namespace ash {
 namespace {
 
 class TestObserver : public PowerStatus::Observer {
  public:
   TestObserver() : power_changed_count_(0) {}
   ~TestObserver() override {}
 
   int power_changed_count() const { return power_changed_count_; }
 
   // PowerStatus::Observer overrides:
   void OnPowerStatusChanged() override { ++power_changed_count_; }
 
  private:
   int power_changed_count_;
 
   DISALLOW_COPY_AND_ASSIGN(TestObserver);
 };
 
 }  // namespace
 
 class PowerStatusTest : public testing::Test {
  public:
-  PowerStatusTest() : power_status_(NULL) {}
+  PowerStatusTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        power_status_(NULL) {}
   ~PowerStatusTest() override {}
 
   void SetUp() override {
     chromeos::DBusThreadManager::Initialize();
     PowerStatus::Initialize();
     power_status_ = PowerStatus::Get();
     test_observer_.reset(new TestObserver);
     power_status_->AddObserver(test_observer_.get());
   }
 
   void TearDown() override {
     power_status_->RemoveObserver(test_observer_.get());
     test_observer_.reset();
     PowerStatus::Shutdown();
     chromeos::DBusThreadManager::Shutdown();
   }
 
  protected:
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   PowerStatus* power_status_;  // Not owned.
   std::unique_ptr<TestObserver> test_observer_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PowerStatusTest);
 };
 
 TEST_F(PowerStatusTest, InitializeAndUpdate) {
   // Test that the initial power supply state should be acquired after
   // PowerStatus is instantiated. This depends on
@@ skipping 214 matching lines @@
   // the battery is 100% full.
   prop.set_battery_percent(99.0);
   power_status_->SetProtoForTesting(prop);
   EXPECT_EQ(11, power_status_->GetBatteryImageInfo().charge_level);
   prop.set_battery_percent(100.0);
   power_status_->SetProtoForTesting(prop);
   EXPECT_EQ(12, power_status_->GetBatteryImageInfo().charge_level);
 }
 
 }  // namespace ash