Use TaskScheduler instead of WorkerPool in x11_hotplug_event_handler.cc.

ui/compositor/test/test_suite.h

Index: ui/compositor/test/test_suite.h
diff --git a/ui/compositor/test/test_suite.h b/ui/compositor/test/test_suite.h
index 09ab669bfd2afdcdcb83b5a9bc3781e3d7e77899..5bc015c7f39485d2dd0f5a7048486015b832b6b4 100644
--- a/ui/compositor/test/test_suite.h
+++ b/ui/compositor/test/test_suite.h
@@ -12,7 +12,9 @@
 #include "base/test/test_suite.h"
 
 namespace base {
-class MessageLoop;
+namespace test {
+class ScopedTaskEnvironment;
+}
 }
 
 namespace ui {
@@ -29,7 +31,7 @@ class CompositorTestSuite : public base::TestSuite {
   void Shutdown() override;
 
  private:
-  std::unique_ptr<base::MessageLoop> message_loop_;
+  std::unique_ptr<base::test::ScopedTaskEnvironment> scoped_task_environment_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositorTestSuite);
 };