Add missing IWYU message_loop.h includes.

remoting/host/chromoting_host_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.
 
 #include "remoting/host/chromoting_host.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "remoting/base/auto_thread_task_runner.h"
 #include "remoting/host/audio_capturer.h"
 #include "remoting/host/chromoting_host_context.h"
 #include "remoting/host/fake_desktop_environment.h"
 #include "remoting/host/fake_mouse_cursor_monitor.h"
 #include "remoting/host/host_mock_objects.h"
 #include "remoting/proto/video.pb.h"
 #include "remoting/protocol/errors.h"
 #include "remoting/protocol/fake_connection_to_client.h"
@@ skipping 352 matching lines @@
   SimulateClientConnection(0, true, false);
 
   std::string channel_name("ChannelName");
   protocol::TransportRoute route;
   EXPECT_CALL(host_status_observer_,
               OnClientRouteChange(session_jid1_, channel_name, _));
   host_->OnSessionRouteChange(get_client(0), channel_name, route);
 }
 
 }  // namespace remoting