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

ios/web_view/internal/web_view_web_main_parts.mm

 // Copyright 2014 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 "ios/web_view/internal/web_view_web_main_parts.h"
 
-#import <Foundation/Foundation.h>
-
 #include "base/base_paths.h"
-#include "base/memory/ptr_util.h"
+#include "base/command_line.h"
 #include "base/path_service.h"
+#include "ios/web_view/internal/app/application_context_impl.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 #include "ui/base/resource/resource_bundle.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace ios_web_view {
 
-WebViewWebMainParts::WebViewWebMainParts() {}
+WebViewWebMainParts::WebViewWebMainParts(
+    const base::CommandLine& parsed_command_line)
+    : parsed_command_line_(parsed_command_line) {}
 
 WebViewWebMainParts::~WebViewWebMainParts() = default;
 
-void WebViewWebMainParts::PreMainMessageLoopRun() {
-  // Initialize resources.
+void WebViewWebMainParts::PreMainMessageLoopStart() {
   l10n_util::OverrideLocaleWithCocoaLocale();
   ui::ResourceBundle::InitSharedInstanceWithLocale(
       std::string(), nullptr, ui::ResourceBundle::DO_NOT_LOAD_COMMON_RESOURCES);
+
   base::FilePath pak_file;
   PathService::Get(base::DIR_MODULE, &pak_file);
   pak_file = pak_file.Append(FILE_PATH_LITERAL("web_view_resources.pak"));
   ui::ResourceBundle::GetSharedInstance().AddDataPackFromPath(
       pak_file, ui::SCALE_FACTOR_NONE);
 }
 
+void WebViewWebMainParts::PreCreateThreads() {
+  application_context_.reset(new ApplicationContextImpl(
+      parsed_command_line_, l10n_util::GetLocaleOverride()));
+  DCHECK_EQ(application_context_.get(), GetApplicationContext());
+
+  // Initialize local state.
+  PrefService* local_state = application_context_->GetLocalState();

[Hiroshi Ichikawa, 2017/05/19 02:37:51]

Optional: Can be in one line:

DCHECK(application_context_->GetLocalState());

[michaeldo, 2017/05/19 22:02:36]

Done.

+  DCHECK(local_state);
+
+  application_context_->PreCreateThreads();
+}
+
+void WebViewWebMainParts::PostMainMessageLoopRun() {
+  // TODO(crbug.com/723869): Shutdown translate.
+  application_context_->StartTearDown();
+}
+
+void WebViewWebMainParts::PostDestroyThreads() {
+  application_context_->PostDestroyThreads();
+}
+
 }  // namespace ios_web_view