[NTP Snippets] Persist remote categories in prefs

components/ntp_snippets/pref_names.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 "components/ntp_snippets/pref_names.h"
 
 namespace ntp_snippets {
 namespace prefs {
 
 const char kEnableSnippets[] = "ntp_snippets.enable";
 
 const char kSnippetHosts[] = "ntp_snippets.hosts";
 
+const char kRemoteSuggestionCategories[] = "ntp_snippets.remote_categories";
+
 const char kSnippetBackgroundFetchingIntervalWifi[] =
     "ntp_snippets.fetching_interval_wifi";
 
 const char kSnippetBackgroundFetchingIntervalFallback[] =
     "ntp_snippets.fetching_interval_fallback";
 
 const char kSnippetFetcherRequestCount[] =
     "ntp.request_throttler.suggestion_fetcher.count";
 const char kSnippetFetcherInteractiveRequestCount[] =
     "ntp.request_throttler.suggestion_fetcher.interactive_count";
@@ skipping 26 matching lines @@
 
 const char kUserClassifierLastTimeToOpenNTP[] =
     "ntp_suggestions.user_classifier.last_time_to_open_ntp";
 const char kUserClassifierLastTimeToShowSuggestions[] =
     "ntp_suggestions.user_classifier.last_time_to_show_suggestions";
 const char kUserClassifierLastTimeToUseSuggestions[] =
     "ntp_suggestions.user_classifier.last_time_to_use_suggestions";
 
 }  // namespace prefs
 }  // namespace ntp_snippets