[ios] Add session saving support to clean skeleton.

ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_factory.h

Index: ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_factory.h
diff --git a/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_factory.h b/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_factory.h
new file mode 100644
index 0000000000000000000000000000000000000000..f2d20de54fafd0ba7500bd57c2da0e979ae62fad
--- /dev/null
+++ b/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_factory.h
@@ -0,0 +1,47 @@
+// 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_SHARED_CHROME_BROWSER_UI_BROWSER_LIST_BROWSER_LIST_SESSION_SERVICE_FACTORY_H_
+#define IOS_SHARED_CHROME_BROWSER_UI_BROWSER_LIST_BROWSER_LIST_SESSION_SERVICE_FACTORY_H_
+
+#include "base/macros.h"
+#include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
+namespace ios {
+class ChromeBrowserState;
+}
+
+class BrowserListSessionService;
+
+// BrowserListSessionServiceFactory attaches BrowserListSessionService to
+// ChromeBrowserState.
+class BrowserListSessionServiceFactory
+    : public BrowserStateKeyedServiceFactory {
+ public:
+  static BrowserListSessionService* GetForBrowserState(
+      ios::ChromeBrowserState* browser_state);
+  static BrowserListSessionServiceFactory* GetInstance();
+
+ private:
+  friend struct base::DefaultSingletonTraits<BrowserListSessionServiceFactory>;
+
+  BrowserListSessionServiceFactory();
+  ~BrowserListSessionServiceFactory() override;
+
+  // BrowserStateKeyedServiceFactory implementation.
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
+      web::BrowserState* context) const override;
+  web::BrowserState* GetBrowserStateToUse(
+      web::BrowserState* context) const override;
+  bool ServiceIsNULLWhileTesting() const override;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserListSessionServiceFactory);
+};
+
+#endif  // IOS_SHARED_CHROME_BROWSER_UI_BROWSER_LIST_BROWSER_LIST_SESSION_SERVICE_FACTORY_H_