Introduce TabRestoreServiceClient and //chrome implementation.

chrome/browser/sessions/chrome_tab_restore_service_client.cc

+// 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.
+
+#include "chrome/browser/sessions/chrome_tab_restore_service_client.h"
+
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sessions/session_service.h"
+#include "chrome/browser/sessions/session_service_factory.h"
+
+ChromeTabRestoreServiceClient::ChromeTabRestoreServiceClient(Profile* profile)
+    : profile_(profile) {}
+
+ChromeTabRestoreServiceClient::~ChromeTabRestoreServiceClient() {}
+
+bool ChromeTabRestoreServiceClient::HasLastSession() {
+#if defined(ENABLE_SESSION_SERVICE)
+  SessionService* session_service =
+      SessionServiceFactory::GetForProfile(profile_);
+  Profile::ExitType exit_type = profile_->GetLastSessionExitType();
+  // The previous session crashed and wasn't restored, or was a forced
+  // shutdown. Both of which won't have notified us of the browser close so
+  // that we need to load the windows from session service (which will have
+  // saved them).
+  return (!profile_->restored_last_session() && session_service &&
+          (exit_type == Profile::EXIT_CRASHED ||
+           exit_type == Profile::EXIT_SESSION_ENDED));
+#else
+  return false;
+#endif
+}
+
+void ChromeTabRestoreServiceClient::GetLastSession(
+    const sessions::GetLastSessionCallback& callback,
+    base::CancelableTaskTracker* tracker) {
+  DCHECK(HasLastSession());
+#if defined(ENABLE_SESSION_SERVICE)
+  SessionServiceFactory::GetForProfile(profile_)
+      ->GetLastSession(callback, tracker);
+#endif
+}