Add missing IWYU message_loop.h includes.

chrome/browser/extensions/api/webstore_private/webstore_private_apitest.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 <vector>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/webstore_private/webstore_private_api.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/extensions/extension_function_test_utils.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/webstore_installer.h"
@@ skipping 395 matching lines @@
 IN_PROC_BROWSER_TEST_F(ExtensionWebstoreGetWebGLStatusTest, Blocked) {
   content::GpuDataManager::GetInstance()->BlacklistWebGLForTesting();
   EXPECT_TRUE(content::GpuDataManager::GetInstance()->IsFeatureBlacklisted(
       gpu::GPU_FEATURE_TYPE_ACCELERATED_WEBGL));
 
   bool webgl_allowed = false;
   RunTest(webgl_allowed);
 }
 
 }  // namespace extensions