Issue 4983 - Get rid of Sleep() in the WebRequest test

include/AdblockPlus/Scheduler.h

 /*
 * This file is part of Adblock Plus <https://adblockplus.org/>,
 * Copyright (C) 2006-2017 eyeo GmbH
 *
 * Adblock Plus is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * Adblock Plus is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include "DefaultWebRequest.h"
-#include <thread>
+#ifndef ADBLOCK_PLUS_SCHEDULER_H
+#define ADBLOCK_PLUS_SCHEDULER_H
 
-using namespace AdblockPlus;
+namespace AdblockPlus
+{
+  /**
+   * Task object which can be passed to `Scheduler` to be executed asynchronously.
+   */
+  typedef std::function<void()> SchedulerTask;
 
-DefaultWebRequest::DefaultWebRequest(std::unique_ptr<DefaultWebRequestSync>&& syncImpl)
-  : syncImpl(std::move(syncImpl))
-{
-
+  /**
+   * Scheduler object executing tasks asynchronously.
+   */
+  typedef std::function<void(const SchedulerTask&)> Scheduler;
 }
-
-DefaultWebRequest::~DefaultWebRequest()
-{
-
-}
-
-void DefaultWebRequest::GET(const std::string& url, const HeaderList& requestHeaders, const GetCallback& getCallback)
-{
-  std::thread([this, url, requestHeaders, getCallback]
-  {
-    getCallback(this->syncImpl->GET(url, requestHeaders));
-  }).detach();
-}
+#endif // ADBLOCK_PLUS_SCHEDULER_H