Add missing IWYU message_loop.h includes.

content/browser/media/capture/web_contents_video_capture_device_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 "content/browser/media/capture/web_contents_video_capture_device.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
 
 #include "base/bind_helpers.h"
 #include "base/debug/debugger.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/test_timeouts.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/browser/renderer_host/render_view_host_factory.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_view_frame_subscriber.h"
@@ skipping 1008 matching lines @@
   for (int i = 0; i < 3; ++i) {
     SimulateRefreshFrameRequest();
     ASSERT_NO_FATAL_FAILURE(client_observer()->WaitForNextColor(SK_ColorGREEN));
   }
 
   device()->StopAndDeAllocate();
 }
 
 }  // namespace
 }  // namespace content