Revert "Use TaskScheduler instead of WorkerPool in x11_hotplug_event_handler.cc."

ui/compositor/test/test_suite.h

 // 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.
 
 #ifndef UI_COMPOSITOR_TEST_TEST_SUITE_H_
 #define UI_COMPOSITOR_TEST_TEST_SUITE_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/test/test_suite.h"
 
 namespace base {
-namespace test {
-class ScopedTaskEnvironment;
-}
+class MessageLoop;
 }
 
 namespace ui {
 namespace test {
 
 class CompositorTestSuite : public base::TestSuite {
  public:
   CompositorTestSuite(int argc, char** argv);
   ~CompositorTestSuite() override;
 
  protected:
   // Overridden from base::TestSuite:
   void Initialize() override;
   void Shutdown() override;
 
  private:
-  std::unique_ptr<base::test::ScopedTaskEnvironment> scoped_task_environment_;
+  std::unique_ptr<base::MessageLoop> message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositorTestSuite);
 };
 
 }  // namespace test
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_TEST_TEST_SUITE_H_