[NTP Snippets] Persist remote categories in prefs

components/ntp_snippets/pref_names.h

Index: components/ntp_snippets/pref_names.h
diff --git a/components/ntp_snippets/pref_names.h b/components/ntp_snippets/pref_names.h
index 4b2a147311adcb65d5dd0cc83ec7ba000a670289..2f9c3778abd5ed44ecdf429b69e077c551dd8784 100644
--- a/components/ntp_snippets/pref_names.h
+++ b/components/ntp_snippets/pref_names.h
@@ -8,10 +8,17 @@
 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[];