[translate] Add translate ranker model loader.

ios/chrome/browser/translate/translate_ranker_factory.cc

+// 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.
+
+#include "ios/chrome/browser/translate/translate_ranker_factory.h"
+
+#include "base/memory/ptr_util.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "components/keyed_service/ios/browser_state_dependency_manager.h"
+#include "components/translate/core/browser/translate_ranker_impl.h"
+#include "ios/chrome/browser/browser_state/browser_state_otr_helper.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+
+namespace translate {
+
+// static
+TranslateRankerFactory* TranslateRankerFactory::GetInstance() {
+  return base::Singleton<TranslateRankerFactory>::get();
+}
+
+// static
+translate::TranslateRanker* TranslateRankerFactory::GetForBrowserState(
+    ios::ChromeBrowserState* state) {
+  return static_cast<TranslateRanker*>(
+      GetInstance()->GetServiceForBrowserState(state, true));
+}
+
+TranslateRankerFactory::TranslateRankerFactory()
+    : BrowserStateKeyedServiceFactory(
+          "TranslateRankerService",
+          BrowserStateDependencyManager::GetInstance()) {}
+
+TranslateRankerFactory::~TranslateRankerFactory() {}
+
+std::unique_ptr<KeyedService> TranslateRankerFactory::BuildServiceInstanceFor(
+    web::BrowserState* context) const {
+  ios::ChromeBrowserState* browser_state =
+      ios::ChromeBrowserState::FromBrowserState(context);
+  return base::MakeUnique<TranslateRankerImpl>(
+      TranslateRankerImpl::GetModelPath(browser_state->GetStatePath()),
+      TranslateRankerImpl::GetModelURL());
+}
+
+web::BrowserState* TranslateRankerFactory::GetBrowserStateToUse(
+    web::BrowserState* context) const {
+  return GetBrowserStateRedirectedInIncognito(context);
+}
+
+}  // namespace translate