[NTP Snippets] Clear the snippets when the user signs out

chrome/browser/ui/webui/snippets_internals_message_handler.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 CHROME_BROWSER_UI_WEBUI_SNIPPETS_INTERNALS_MESSAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SNIPPETS_INTERNALS_MESSAGE_HANDLER_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 16 matching lines @@
 
  private:
   // content::WebUIMessageHandler:
   void RegisterMessages() override;
 
   // ntp_snippets::NTPSnippetsServiceObserver:
   // Send everytime the service loads a new set of data.
   void NTPSnippetsServiceLoaded() override;
   // Send when the service is shutting down.
   void NTPSnippetsServiceShutdown() override;
+  // Sent every time the service has its data sources cleared.
+  void NTPSnippetsServiceCleared() override;
 
   void HandleLoaded(const base::ListValue* args);
   void HandleClear(const base::ListValue* args);
   void HandleDump(const base::ListValue* args);
   void HandleClearDiscarded(const base::ListValue* args);
   void HandleDownload(const base::ListValue* args);
 
   void SendInitialData();
   void SendSnippets();
   void SendDiscardedSnippets();
   void SendHosts();
   void SendJson(const std::string& json);
   void SendBoolean(const std::string& name, bool value);
   void SendString(const std::string& name, const std::string& value);
 
   ScopedObserver<ntp_snippets::NTPSnippetsService,
                  ntp_snippets::NTPSnippetsServiceObserver> observer_;
 
   // Tracks whether we can already send messages to the page.
   bool dom_loaded_;
 
   ntp_snippets::NTPSnippetsService* ntp_snippets_service_;
 
   DISALLOW_COPY_AND_ASSIGN(SnippetsInternalsMessageHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SNIPPETS_INTERNALS_MESSAGE_HANDLER_H_