Use ScopedTaskEnvironment instead of MessageLoopForUI in ui tests.

ui/views/cocoa/bridged_native_widget_unittest.mm

 // Copyright 2014 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 "ui/views/cocoa/bridged_native_widget.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
 
 #import "base/mac/foundation_util.h"
 #import "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/macros.h"
-#include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #import "testing/gtest_mac.h"
 #import "ui/base/cocoa/window_size_constants.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/test/material_design_controller_test_api.h"
 #include "ui/events/test/cocoa_test_event_utils.h"
 #import "ui/gfx/mac/coordinate_conversion.h"
 #import "ui/gfx/test/ui_cocoa_test_helper.h"
 #import "ui/views/cocoa/bridged_content_view.h"
 #import "ui/views/cocoa/native_widget_mac_nswindow.h"
@@ skipping 326 matching lines @@
   void TestEditingCommands(NSArray* selectors, TestCase cases = TestCase::ALL);
 
   std::unique_ptr<views::View> view_;
 
   // Weak. Owned by bridge().
   BridgedContentView* ns_view_;
 
   // An NSTextView which helps set the expectations for our tests.
   base::scoped_nsobject<NSTextView> dummy_text_view_;
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BridgedNativeWidgetTest);
 };
 
-BridgedNativeWidgetTest::BridgedNativeWidgetTest() {
-}
+BridgedNativeWidgetTest::BridgedNativeWidgetTest()
+    : scoped_task_environment_(
+          base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
 
 BridgedNativeWidgetTest::~BridgedNativeWidgetTest() {
 }
 
 void BridgedNativeWidgetTest::InstallTextField(
     const base::string16& text,
     ui::TextInputType text_input_type) {
   Textfield* textfield = new Textfield();
   textfield->SetText(text);
   textfield->SetTextInputType(text_input_type);
@@ skipping 940 matching lines @@
   [center postNotificationName:NSWindowDidExitFullScreenNotification
                         object:window];
   EXPECT_EQ(1, [window ignoredToggleFullScreenCount]);  // No change.
   EXPECT_FALSE(bridge()->target_fullscreen_state());
 
   widget_->CloseNow();
 }
 
 }  // namespace test
 }  // namespace views