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

ios/web_view/internal/app/application_context_impl.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_IMPL_H_
+#define IOS_WEB_VIEW_INTERNAL_APP_APPLICATION_CONTEXT_IMPL_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
+#include "ios/web_view/internal/app/application_context.h"
+
+namespace base {
+class CommandLine;
+class FilePath;
+class SequencedTaskRunner;
+}
+
+class ApplicationContextImpl : public ApplicationContext {
+ public:
+  ApplicationContextImpl(const base::CommandLine& command_line,
+                         const std::string& locale);
+  ~ApplicationContextImpl() override;
+
+  // Called before the browser threads are created.
+  void PreCreateThreads();
+
+  // Most cleanup is done by these functions, driven from WebViewWebMainParts

[Eugene But (OOO till 7-30), 2017/05/18 23:54:55]

Please explain what these methods do, instead of where they are currently
called.

[michaeldo, 2017/05/19 22:02:35]

Done.

+  // rather than in the destructor, so that we can interleave cleanup with

[Eugene But (OOO till 7-30), 2017/05/18 23:54:55]

nit: Avoid "we" in the comments (go/avoidwe)

[michaeldo, 2017/05/19 22:02:35]

Done.

+  // threads being stopped.
+  void StartTearDown();
+  void PostDestroyThreads();
+
+  // ApplicationContext implementation.
+  PrefService* GetLocalState() override;
+  net_log::ChromeNetLog* GetNetLog() override;
+  net::URLRequestContextGetter* GetSystemURLRequestContext() override;
+  const std::string& GetApplicationLocale() override;
+  WebViewIOThread* GetWebViewIOThread() override;
+
+ private:
+  static base::FilePath LocalStatePath();

[Eugene But (OOO till 7-30), 2017/05/18 23:54:55]

GetLocalStatePath ?

[michaeldo, 2017/05/19 22:02:35]

Done.

+
+  // Sets the locale used by the application.
+  void SetApplicationLocale(const std::string& locale);
+
+  // Create the local state.

[Eugene But (OOO till 7-30), 2017/05/18 23:54:55]

This comment simply repeats the method name. Would it be bette to explain what
"Local State" is?

[michaeldo, 2017/05/19 22:02:35]

Updated comment here and in application_context.h explaining local state concept
as preferences.

+  void CreateLocalState();
+
+  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_;
+
+  bool created_local_state_;

[Eugene But (OOO till 7-30), 2017/05/18 23:54:55]

Why do we need a boolean? Can we check if local_state_ is not null instead?

[michaeldo, 2017/05/23 22:38:36]

After looking into it, I removed the bool as it isn't necessary. (Especially
with the DCHECK that validates !local_state) I'm not sure why it existed in
other ApplicationContextImpl.

+
+  DISALLOW_COPY_AND_ASSIGN(ApplicationContextImpl);
+};
+
+#endif  // IOS_WEB_VIEW_INTERNAL_APP_APPLICATION_CONTEXT_IMPL_H_