[translate] Add translate ranker model loader.

ios/web_view/internal/translate/web_view_translate_ranker_factory.cc

+// Copyright 2016 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/web_view/internal/translate/web_view_translate_ranker_factory.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/memory/singleton.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/web_view/internal/pref_names.h"
+#include "ios/web_view/internal/web_view_browser_state.h"
+
+namespace ios_web_view {
+
+// static
+WebViewTranslateRankerFactory* WebViewTranslateRankerFactory::GetInstance() {
+  return base::Singleton<WebViewTranslateRankerFactory>::get();
+}
+
+// static
+translate::TranslateRanker* WebViewTranslateRankerFactory::GetForBrowserState(
+    WebViewBrowserState* state) {
+  return static_cast<translate::TranslateRanker*>(
+      GetInstance()->GetServiceForBrowserState(state, true));
+}
+
+WebViewTranslateRankerFactory::WebViewTranslateRankerFactory()
+    : BrowserStateKeyedServiceFactory(
+          "TranslateRankerService",
+          BrowserStateDependencyManager::GetInstance()) {}
+
+WebViewTranslateRankerFactory::~WebViewTranslateRankerFactory() {}
+
+std::unique_ptr<KeyedService>
+WebViewTranslateRankerFactory::BuildServiceInstanceFor(
+    web::BrowserState* context) const {
+  WebViewBrowserState* web_view_browser_state =
+      WebViewBrowserState::FromBrowserState(context);
+  return base::MakeUnique<translate::TranslateRankerImpl>(
+      translate::TranslateRankerImpl::GetModelPath(
+          web_view_browser_state->GetStatePath()),
+      translate::TranslateRankerImpl::GetModelURL());
+}
+
+}  // namespace ios_web_view