[ios] Add session saving support to clean skeleton.

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

Index: ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_impl.h
diff --git a/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_impl.h b/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..ed69309acb2622f93c8f537f9152ed434bb21617
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+++ b/ios/shared/chrome/browser/ui/browser_list/browser_list_session_service_impl.h
@@ -0,0 +1,60 @@
+// 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_IMPL_H_
+#define IOS_SHARED_CHROME_BROWSER_UI_BROWSER_LIST_BROWSER_LIST_SESSION_SERVICE_IMPL_H_
+
+#import <Foundation/Foundation.h>
+
+#include <memory>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#import "ios/shared/chrome/browser/ui/browser_list/browser_list_session_service.h"
+#import "ios/web/public/web_state/web_state.h"
+
+class BrowserList;
+class BrowserListObserver;
+@class CRWSessionStorage;
+@class SessionServiceIOS;
+
+namespace web {
+class WebState;
+}
+
+// Implementation of BrowserListSessionService that automatically track the
+// active WebStates of |browser_list| and save the session when the active
+// WebState changes or a new navigation item is committed.
+class BrowserListSessionServiceImpl : public BrowserListSessionService {
+ public:
+  // Callback used to create WebStates when restoring a session.
+  using CreateWebStateCallback =
+      base::RepeatingCallback<std::unique_ptr<web::WebState>(
+          CRWSessionStorage*)>;
+
+  BrowserListSessionServiceImpl(BrowserList* browser_list,
+                                NSString* session_directory,
+                                SessionServiceIOS* session_service,
+                                const CreateWebStateCallback& create_web_state);
+  ~BrowserListSessionServiceImpl() override;
+
+  // BrowserListSessionService implementation.
+  bool RestoreSession() override;
+  void ScheduleLastSessionDeletion() override;
+  void ScheduleSaveSession(bool immediately) override;
+
+  // KeyedService implementation.
+  void Shutdown() override;
+
+ private:
+  BrowserList* browser_list_;
+  __strong NSString* session_directory_;
+  __strong SessionServiceIOS* session_service_;
+  CreateWebStateCallback create_web_state_;
+  std::unique_ptr<BrowserListObserver> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserListSessionServiceImpl);
+};
+
+#endif  // IOS_SHARED_CHROME_BROWSER_UI_BROWSER_LIST_BROWSER_LIST_SESSION_SERVICE_IMPL_H_