[NTP Snippets] Don't reschedule background fetching on every startup

components/ntp_snippets/ntp_snippets_service.cc

Index: components/ntp_snippets/ntp_snippets_service.cc
diff --git a/components/ntp_snippets/ntp_snippets_service.cc b/components/ntp_snippets/ntp_snippets_service.cc
index 20995ee0a75cb927314376771ea85492b42530b1..2313a15bf45cfcab344f8aeee3f6a83d5039e739 100644
--- a/components/ntp_snippets/ntp_snippets_service.cc
+++ b/components/ntp_snippets/ntp_snippets_service.cc
@@ -232,6 +232,9 @@ NTPSnippetsService::~NTPSnippetsService() {
 // static
 void NTPSnippetsService::RegisterProfilePrefs(PrefRegistrySimple* registry) {
   registry->RegisterListPref(prefs::kSnippetHosts);
+  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalWifi, 0);
+  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalFallback,
+                              0);
 
   NTPSnippetsStatusService::RegisterProfilePrefs(registry);
 }
@@ -268,21 +271,40 @@ void NTPSnippetsService::FetchSnippetsFromHosts(
                                             interactive_request);
 }
 
-void NTPSnippetsService::RescheduleFetching() {
+void NTPSnippetsService::RescheduleFetching(bool force) {
   // The scheduler only exists on Android so far, it's null on other platforms.
   if (!scheduler_)
     return;
 
-  // If we're NOT_INITED, we don't know whether to schedule or un-schedule.
-  // We'll reschedule on the next state change anyway, so do nothing here.
-  if (state_ == State::NOT_INITED)
-    return;
-
   if (ready()) {
-    scheduler_->Schedule(GetFetchingIntervalWifi(),
-                         GetFetchingIntervalFallback());
+    base::TimeDelta old_interval_wifi =
+        base::TimeDelta::FromInternalValue(pref_service_->GetInt64(
+            prefs::kSnippetBackgroundFetchingIntervalWifi));
+    base::TimeDelta old_interval_fallback =
+        base::TimeDelta::FromInternalValue(pref_service_->GetInt64(
+            prefs::kSnippetBackgroundFetchingIntervalFallback));
+    base::TimeDelta interval_wifi = GetFetchingIntervalWifi();
+    base::TimeDelta interval_fallback = GetFetchingIntervalFallback();
+    if (force || interval_wifi != old_interval_wifi ||
+        interval_fallback != old_interval_fallback) {
+      scheduler_->Schedule(interval_wifi, interval_fallback);
+      pref_service_->SetInt64(prefs::kSnippetBackgroundFetchingIntervalWifi,
+                              interval_wifi.ToInternalValue());
+      pref_service_->SetInt64(
+          prefs::kSnippetBackgroundFetchingIntervalFallback,
+          interval_fallback.ToInternalValue());
+    }
   } else {
-    scheduler_->Unschedule();
+    // If we're NOT_INITED, we don't know whether to schedule or un-schedule.
+    // If |force| is false, all is well: We'll reschedule on the next state
+    // change anyway. If it's true, then unschedule here, to make sure that the
+    // next reschedule actually happens.
+    if (state_ != State::NOT_INITED || force) {
+      scheduler_->Unschedule();
+      pref_service_->ClearPref(prefs::kSnippetBackgroundFetchingIntervalWifi);
+      pref_service_->ClearPref(
+          prefs::kSnippetBackgroundFetchingIntervalFallback);
+    }
   }
 }
 
@@ -610,7 +632,7 @@ void NTPSnippetsService::OnFetchFinished(
   // succeeded, and also that we don't do a background fetch immediately after
   // a user-initiated one.
   if (snippets)
-    RescheduleFetching();
+    RescheduleFetching(true);
 }
 
 void NTPSnippetsService::ArchiveSnippets(Category category,
@@ -990,10 +1012,7 @@ void NTPSnippetsService::EnterState(State state) {
   }
 
   // Schedule or un-schedule background fetching after each state change.
-  // TODO(treib): This resets all currently scheduled fetches on each Chrome
-  // start. Maybe store the currently scheduled values in prefs, and only
-  // reschedule if they have changed? crbug.com/646842
-  RescheduleFetching();
+  RescheduleFetching(false);
 }
 
 void NTPSnippetsService::NotifyNewSuggestions() {