Add missing IWYU message_loop.h includes.

content/browser/gpu/gpu_process_host.cc

 // 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.
 
 #include "content/browser/gpu/gpu_process_host.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <list>
 #include <utility>
 
 #include "base/base64.h"
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sha1.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "components/tracing/common/tracing_switches.h"
 #include "content/browser/browser_child_process_host_impl.h"
 #include "content/browser/browser_main_loop.h"
@@ skipping 1176 matching lines @@
   if (!cache.get())
     return;
 
   cache->set_shader_loaded_callback(base::Bind(&GpuProcessHost::LoadedShader,
                                                weak_ptr_factory_.GetWeakPtr()));
 
   client_id_to_shader_cache_[client_id] = cache;
 }
 
 }  // namespace content