Introduce TabRestoreServiceClient and //chrome implementation.

chrome/browser/sessions/chrome_tab_restore_service_client.h

+// Copyright 2015 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 CHROME_BROWSER_SESSIONS_CHROME_TAB_RESTORE_SERVICE_CLIENT_H_
+#define CHROME_BROWSER_SESSIONS_CHROME_TAB_RESTORE_SERVICE_CLIENT_H_
+
+#include "base/basictypes.h"
+#include "components/sessions/core/tab_restore_service_client.h"
+
+class Profile;
+
+// ChromeTabRestoreServiceClient provides an implementation of
+// TabRestoreServiceClient that depends on chrome/.
+class ChromeTabRestoreServiceClient : public sessions::TabRestoreServiceClient {
+ public:
+  explicit ChromeTabRestoreServiceClient(Profile* profile);
+  ~ChromeTabRestoreServiceClient() override;
+
+ private:
+  // TabRestoreServiceClient:
+  bool HasLastSession() override;
+  void GetLastSession(const sessions::GetLastSessionCallback& callback,
+                      base::CancelableTaskTracker* tracker) override;
+
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeTabRestoreServiceClient);
+};
+
+#endif  // CHROME_BROWSER_SESSIONS_CHROME_TAB_RESTORE_SERVICE_CLIENT_H_