Add missing IWYU message_loop.h includes.

device/hid/hid_connection_unittest.cc

 // Copyright (c) 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 "device/hid/hid_connection.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/scoped_observer.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/test_io_thread.h"
 #include "device/hid/hid_service.h"
 #include "device/test/test_device_client.h"
 #include "device/test/usb_test_gadget.h"
 #include "device/usb/usb_device.h"
 #include "net/base/io_buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 179 matching lines @@
     ASSERT_EQ(0, read_callback.buffer()->data()[0]);
     for (unsigned char j = 1; j < kBufferSize; ++j) {
       ASSERT_EQ(i + j - 1, read_callback.buffer()->data()[j]);
     }
   }
 
   conn->Close();
 }
 
 }  // namespace device