Remove unused thread.h include in trace_event_impl.h and fix IWUU.

ui/ozone/public/ozone_gpu_test_helper.cc

 // 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.
 
 #include "ui/ozone/public/ozone_gpu_test_helper.h"
 
+#include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_sender.h"
 #include "ipc/message_filter.h"
 #include "ui/ozone/public/gpu_platform_support_host.h"
 #include "ui/ozone/public/ozone_platform.h"
 
 namespace ui {
 
@@ skipping 116 matching lines @@
                             base::Unretained(fake_gpu_process_.get())));
 
   fake_gpu_process_host_.reset(new FakeGpuProcessHost(
       gpu_task_runner, io_helper_thread_->task_runner()));
   fake_gpu_process_host_->Init();
 
   return true;
 }
 
 }  // namespace ui