DownloadService: Only call getScheduler once

The second getScheduler() call violates the documentation of
the class, which states that getScheduler() is not called if
foregroundNotificationId if FOREGROUND_NOTIFICATION_ID_NONE.
Presumably implementing subclasses would return null, in which
case this didn't do any harm, but we should make sure the
implementation behaves as documented regardless.

PiperOrigin-RevId: 397167603

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadService.java

@@ -178,6 +178,7 @@ public abstract class DownloadService extends Service {
   @StringRes private final int channelNameResourceId;
   @StringRes private final int channelNameResourceId;
   @StringRes private final int channelDescriptionResourceId;
   @StringRes private final int channelDescriptionResourceId;
 
 
+  private @MonotonicNonNull Scheduler scheduler;
   private @MonotonicNonNull DownloadManager downloadManager;
   private @MonotonicNonNull DownloadManager downloadManager;
   private int lastStartId;
   private int lastStartId;
   private boolean startedInForeground;
   private boolean startedInForeground;
@@ -582,6 +583,9 @@ public abstract class DownloadService extends Service {
     if (downloadManagerHelper == null) {
     if (downloadManagerHelper == null) {
       boolean foregroundAllowed = foregroundNotificationUpdater != null;
       boolean foregroundAllowed = foregroundNotificationUpdater != null;
       @Nullable Scheduler scheduler = foregroundAllowed ? getScheduler() : null;
       @Nullable Scheduler scheduler = foregroundAllowed ? getScheduler() : null;
+      if (scheduler != null) {
+        this.scheduler = scheduler;
+      }
       downloadManager = getDownloadManager();
       downloadManager = getDownloadManager();
       downloadManager.resumeDownloads();
       downloadManager.resumeDownloads();
       downloadManagerHelper =
       downloadManagerHelper =
@@ -589,6 +593,9 @@ public abstract class DownloadService extends Service {
               getApplicationContext(), downloadManager, foregroundAllowed, scheduler, clazz);
               getApplicationContext(), downloadManager, foregroundAllowed, scheduler, clazz);
       downloadManagerHelpers.put(clazz, downloadManagerHelper);
       downloadManagerHelpers.put(clazz, downloadManagerHelper);
     } else {
     } else {
+      if (downloadManagerHelper.scheduler != null) {
+        scheduler = downloadManagerHelper.scheduler;
+      }
       downloadManager = downloadManagerHelper.downloadManager;
       downloadManager = downloadManagerHelper.downloadManager;
     }
     }
     downloadManagerHelper.attachService(this);
     downloadManagerHelper.attachService(this);
@@ -658,7 +665,6 @@ public abstract class DownloadService extends Service {
         if (requirements == null) {
         if (requirements == null) {
           Log.e(TAG, "Ignored SET_REQUIREMENTS: Missing " + KEY_REQUIREMENTS + " extra");
           Log.e(TAG, "Ignored SET_REQUIREMENTS: Missing " + KEY_REQUIREMENTS + " extra");
         } else {
         } else {
-          @Nullable Scheduler scheduler = getScheduler();
           if (scheduler != null) {
           if (scheduler != null) {
             Requirements supportedRequirements = scheduler.getSupportedRequirements(requirements);
             Requirements supportedRequirements = scheduler.getSupportedRequirements(requirements);
             if (!supportedRequirements.equals(requirements)) {
             if (!supportedRequirements.equals(requirements)) {