Replace `Dummy` with `Placeholder`

`Dummy` is a non inclusive language.

PiperOrigin-RevId: 547815680
(cherry picked from commit 74c3ae24e98c8e445f14b3cdd9d78186d41f2b94)

library/core/src/main/java/com/google/android/exoplayer2/upstream/LoaderErrorThrower.java

@@ -50,7 +50,7 @@ public interface LoaderErrorThrower {
   void maybeThrowError(int minRetryCount) throws IOException;
 
   /** A {@link LoaderErrorThrower} that never throws. */
-  final class Dummy implements LoaderErrorThrower {
+  final class Placeholder implements LoaderErrorThrower {
 
     @Override
     public void maybeThrowError() {

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -476,7 +476,7 @@ public final class DashMediaSource extends BaseMediaSource {
       manifestCallback = null;
       refreshManifestRunnable = null;
       simulateManifestRefreshRunnable = null;
-      manifestLoadErrorThrower = new LoaderErrorThrower.Dummy();
+      manifestLoadErrorThrower = new LoaderErrorThrower.Placeholder();
     } else {
       manifestCallback = new ManifestCallback();
       manifestLoadErrorThrower = new ManifestLoadErrorThrower();

library/dash/src/test/java/com/google/android/exoplayer2/source/dash/DefaultDashChunkSourceTest.java

@@ -86,7 +86,7 @@ public class DefaultDashChunkSourceTest {
     DefaultDashChunkSource chunkSource =
         new DefaultDashChunkSource(
             BundledChunkExtractor.FACTORY,
-            new LoaderErrorThrower.Dummy(),
+            new LoaderErrorThrower.Placeholder(),
             manifest,
             new BaseUrlExclusionList(),
             /* periodIndex= */ 0,
@@ -136,7 +136,7 @@ public class DefaultDashChunkSourceTest {
     DefaultDashChunkSource chunkSource =
         new DefaultDashChunkSource(
             BundledChunkExtractor.FACTORY,
-            new LoaderErrorThrower.Dummy(),
+            new LoaderErrorThrower.Placeholder(),
             manifest,
             new BaseUrlExclusionList(),
             /* periodIndex= */ 0,
@@ -444,7 +444,7 @@ public class DefaultDashChunkSourceTest {
             new DefaultBandwidthMeter.Builder(ApplicationProvider.getApplicationContext()).build());
     return new DefaultDashChunkSource(
         BundledChunkExtractor.FACTORY,
-        new LoaderErrorThrower.Dummy(),
+        new LoaderErrorThrower.Placeholder(),
         manifest,
         new BaseUrlExclusionList(new Random(/* seed= */ 1234)),
         /* periodIndex= */ 0,

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java

@@ -407,7 +407,7 @@ public final class SsMediaSource extends BaseMediaSource
     drmSessionManager.setPlayer(/* playbackLooper= */ Looper.myLooper(), getPlayerId());
     drmSessionManager.prepare();
     if (sideloadedManifest) {
-      manifestLoaderErrorThrower = new LoaderErrorThrower.Dummy();
+      manifestLoaderErrorThrower = new LoaderErrorThrower.Placeholder();
       processManifest();
     } else {
       manifestDataSource = manifestDataSourceFactory.createDataSource();