Add missing IWYU message_loop.h includes.

media/gpu/video_decode_accelerator_unittest.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.
 //
 // The bulk of this file is support code; sorry about that.  Here's an overview
 // to hopefully help readers of this code:
 // - RenderingHelper is charged with interacting with X11/{EGL/GLES2,GLX/GL} or
 //   Win/EGL.
 // - ClientState is an enum for the state of the decode client used by the test.
 // - ClientStateNotification is a barrier abstraction that allows the test code
@@ skipping 20 matching lines @@
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/format_macros.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/md5.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/process/process_handle.h"
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringize_macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
@@ skipping 1864 matching lines @@
       media::g_thumbnail_output_dir = base::FilePath(it->second.c_str());
     }
   }
 
   base::ShadowingAtExitManager at_exit_manager;
 
   return base::LaunchUnitTestsSerially(
       argc, argv,
       base::Bind(&media::VDATestSuite::Run, base::Unretained(&test_suite)));
 }