[NTP Snippets] Remove deprecated prefs

BUG=617585

Review-Url: https://codereview.chromium.org/2130363002
Cr-Commit-Position: refs/heads/master@{#404616}

components/ntp_snippets/ntp_snippets_service.cc

@@ -204,9 +204,6 @@ NTPSnippetsService::NTPSnippetsService(
       database_(std::move(database)),
       snippets_status_service_(std::move(status_service)),
       fetch_after_load_(false) {
-  // TODO(dgn) should be removed after branch point (https://crbug.com/617585).
-  ClearDeprecatedPrefs();
-
   if (!enabled || database_->IsErrorState()) {
     // Don't even bother loading the database.
     EnterState(State::SHUT_DOWN);
@@ -228,8 +225,6 @@ NTPSnippetsService::~NTPSnippetsService() {
 
 // static
 void NTPSnippetsService::RegisterProfilePrefs(PrefRegistrySimple* registry) {
-  registry->RegisterListPref(prefs::kDeprecatedSnippets);
-  registry->RegisterListPref(prefs::kDeprecatedDiscardedSnippets);
   registry->RegisterListPref(prefs::kSnippetHosts);
 }
 
@@ -762,9 +757,4 @@ void NTPSnippetsService::EnterState(State state) {
   }
 }
 
-void NTPSnippetsService::ClearDeprecatedPrefs() {
-  pref_service_->ClearPref(prefs::kDeprecatedSnippets);
-  pref_service_->ClearPref(prefs::kDeprecatedDiscardedSnippets);
-}
-
 }  // namespace ntp_snippets

components/ntp_snippets/ntp_snippets_service.h

@@ -252,8 +252,6 @@ class NTPSnippetsService : public KeyedService,
   // directly, use |EnterState| instead.
   void EnterStateShutdown();
 
-  void ClearDeprecatedPrefs();
-
   State state_;
 
   PrefService* pref_service_;

components/ntp_snippets/pref_names.cc

@@ -7,9 +7,6 @@
 namespace ntp_snippets {
 namespace prefs {
 
-const char kDeprecatedSnippets[] = "ntp_snippets.snippets";
-const char kDeprecatedDiscardedSnippets[] = "ntp_snippets.discarded_snippets";
-
 const char kSnippetHosts[] = "ntp_snippets.hosts";
 
 }  // namespace prefs

components/ntp_snippets/pref_names.h

@@ -8,10 +8,6 @@
 namespace ntp_snippets {
 namespace prefs {
 
-// TODO(treib): Completely remove these after M53.
-extern const char kDeprecatedSnippets[];
-extern const char kDeprecatedDiscardedSnippets[];
-
 extern const char kSnippetHosts[];
 
 }  // namespace prefs