Initialize ios/web_view translate with a system-wide URLRequestContext.

ios/web_view/internal/app/application_context.h

+// Copyright 2017 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.
+
+#ifndef IOS_WEB_VIEW_INTERNAL_APP_APPLICATION_CONTEXT_H_
+#define IOS_WEB_VIEW_INTERNAL_APP_APPLICATION_CONTEXT_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+class FilePath;
+class SequencedTaskRunner;
+}
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace net_log {
+class ChromeNetLog;
+}
+
+class PrefService;
+
+namespace ios_web_view {
+
+class WebViewIOThread;
+
+// Exposes application global state objects.
+class ApplicationContext {
+ public:
+  static ApplicationContext* GetInstance();
+
+  // Gets the preferences associated with this application.
+  PrefService* GetLocalState();
+
+  // Gets the URL request context associated with this application.
+  net::URLRequestContextGetter* GetSystemURLRequestContext();
+
+  // Gets the locale used by the application.
+  const std::string& GetApplicationLocale();
+
+  // Creates state tied to application threads.

[Eugene But (OOO till 7-30), 2017/05/31 16:25:34]

When and why this should be called? Please specify in the comments 

[michaeldo, 2017/05/31 21:03:43]

Done.

+  void PreCreateThreads();
+
+  // Saves applicaiton context state.

[Eugene But (OOO till 7-30), 2017/05/31 16:25:34]

ditto

[michaeldo, 2017/05/31 21:03:42]

Done.

+  void SaveState();
+
+  // Destroys state tied to application threads.

[Eugene But (OOO till 7-30), 2017/05/31 16:25:34]

ditto

[michaeldo, 2017/05/31 21:03:43]

Done.

+  void PostDestroyThreads();
+
+ private:
+  ApplicationContext();
+  ~ApplicationContext();
+  friend struct base::DefaultSingletonTraits<ApplicationContext>;
+
+  // Gets the ChromeNetLog.
+  net_log::ChromeNetLog* GetNetLog();
+
+  // Gets the WebViewIOThread.
+  WebViewIOThread* GetWebViewIOThread();
+
+  // Returns the path to the application level preferences.
+  static base::FilePath GetLocalStatePath();
+
+  // Sets the locale used by the application.
+  void SetApplicationLocale(const std::string& locale);
+
+  THREAD_CHECKER(thread_checker_);
+  std::unique_ptr<PrefService> local_state_;
+  std::unique_ptr<net_log::ChromeNetLog> net_log_;
+  std::unique_ptr<WebViewIOThread> web_view_io_thread_;
+  std::string application_locale_;
+
+  // Sequenced task runner for local state related I/O tasks.
+  const scoped_refptr<base::SequencedTaskRunner> local_state_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ApplicationContext);
+};
+
+}  // namespace ios_web_view
+
+#endif  // IOS_WEB_VIEW_INTERNAL_APP_APPLICATION_CONTEXT_H_