[NTP Snippets] Persist remote categories in prefs

components/ntp_snippets/pref_names.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_PREF_NAMES_H_
 #define COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_
 
 namespace ntp_snippets {
 namespace prefs {
 
+// If set to false, remote suggestions are completely disabled. This is set by
+// an enterprise policy.
 extern const char kEnableSnippets[];
 
+// TODO(treib): Remove this after M56.
 extern const char kSnippetHosts[];
 
+// The pref name under which remote suggestion categories (including their ID
+// and title) are stored.
+extern const char kRemoteSuggestionCategories[];
+
 // The pref name for the currently-scheduled background fetching interval when
 // there is WiFi connectivity.
 extern const char kSnippetBackgroundFetchingIntervalWifi[];
 // The pref name for the currently-scheduled background fetching interval when
 // there is no WiFi connectivity.
 extern const char kSnippetBackgroundFetchingIntervalFallback[];
 
 // The pref name for today's count of NTPSnippetsFetcher requests, so far.
 extern const char kSnippetFetcherRequestCount[];
 // The pref name for today's count of NTPSnippetsFetcher interactive requests.
@@ skipping 33 matching lines @@
 extern const char kUserClassifierLastTimeToOpenNTP[];
 // The pref name for the last time content suggestions were shown to the user.
 extern const char kUserClassifierLastTimeToShowSuggestions[];
 // The pref name for the last time content suggestions were used by the user.
 extern const char kUserClassifierLastTimeToUseSuggestions[];
 
 }  // namespace prefs
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_PREF_NAMES_H_