Add missing IWYU message_loop.h includes.

components/image_fetcher/ios/ios_image_data_fetcher_wrapper_unittest.mm

 // Copyright 2011 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.
 
 #import "components/image_fetcher/ios/ios_image_data_fetcher_wrapper.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/ios/ios_util.h"
 #include "base/mac/scoped_block.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #import "components/image_fetcher/ios/webp_decoder.h"
 #include "net/http/http_response_headers.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request_test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 195 matching lines @@
   EXPECT_TRUE(called_);
 }
 
 TEST_F(IOSImageDataFetcherWrapperTest, TestCallbacksNotCalledDuringDeletion) {
   image_fetcher_->FetchImageDataWebpDecoded(GURL(kTestUrl), callback_);
   image_fetcher_.reset();
   EXPECT_FALSE(called_);
 }
 
 }  // namespace image_fetcher