Foreign tab suggestions should update when disabling sync or signing out.

components/ntp_snippets/sessions/tab_delegate_sync_adapter.h

 // 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.
 
 #ifndef COMPONENTS_NTP_SNIPPETS_SESSIONS_TAB_DELEGATE_SYNC_ADAPTER_H_
 #define COMPONENTS_NTP_SNIPPETS_SESSIONS_TAB_DELEGATE_SYNC_ADAPTER_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 27 matching lines @@
   // syncer::SyncServiceObserver implementation.
   void OnStateChanged() override;
   void OnSyncConfigurationCompleted() override;
   void OnForeignSessionUpdated() override;
 
   void InvokeCallback();
 
   syncer::SyncService* sync_service_;
   base::Closure change_callback_;
 
+  // Represents whether there was session data the last time |change_callback_|
+  // was invoked.
+  bool had_session_data_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(TabDelegateSyncAdapter);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_SESSIONS_TAB_DELEGATE_SYNC_ADAPTER_H_