Add missing IWYU message_loop.h includes.

ipc/ipc_mojo_perftest.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 <stddef.h>
 #include <memory>
 
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/process/process_metrics.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/perf_time_logger.h"
 #include "base/test/test_io_thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "ipc/ipc_channel_mojo.h"
 #include "ipc/ipc_test.mojom.h"
 #include "ipc/ipc_test_base.h"
@@ skipping 753 matching lines @@
   RunSingleThreadPostTaskPingPongServer();
 }
 
 // Sends the same data as above without using PostTask to the same thread.
 TEST_F(CallbackPerfTest, SingleThreadNoPostTaskPingPong) {
   RunSingleThreadNoPostTaskPingPongServer();
 }
 
 }  // namespace
 }  // namespace IPC