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

chrome/browser/ui/webui/snippets_internals_message_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/snippets_internals_message_handler.h"
 
 #include <memory>
 #include <set>
 #include <vector>
 
@@ skipping 60 matching lines @@
   if (!dom_loaded_) return;
 
   SendSnippets();
   SendDiscardedSnippets();
 
   web_ui()->CallJavascriptFunction(
       "chrome.SnippetsInternals.receiveJson",
       base::StringValue(ntp_snippets_service_->last_json()));
 }
 
+void SnippetsInternalsMessageHandler::NTPSnippetsServiceCleared() {}
+
 void SnippetsInternalsMessageHandler::RegisterMessages() {
   // additional initialization (web_ui() does not work from the constructor)
   ntp_snippets_service_ = NTPSnippetsServiceFactory::GetInstance()->
       GetForProfile(Profile::FromWebUI(web_ui()));
   observer_.Add(ntp_snippets_service_);
 
   web_ui()->RegisterMessageCallback(
       "loaded",
       base::Bind(&SnippetsInternalsMessageHandler::HandleLoaded,
                  base::Unretained(this)));
@@ skipping 145 matching lines @@
 }
 
 void SnippetsInternalsMessageHandler::SendString(const std::string& name,
                                                  const std::string& value) {
   base::StringValue string_name(name);
   base::StringValue string_value(value);
 
   web_ui()->CallJavascriptFunction("chrome.SnippetsInternals.receiveProperty",
                                    string_name, string_value);
 }