Playlist API: add Playlist and PlaylistTest

PiperOrigin-RevId: 278875587

library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java → library/core/src/main/java/com/google/android/exoplayer2/AbstractConcatenatedTimeline.java

@@ -13,16 +13,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.google.android.exoplayer2.source;
+package com.google.android.exoplayer2;
 
 import android.util.Pair;
-import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.Player;
-import com.google.android.exoplayer2.Timeline;
+import com.google.android.exoplayer2.source.ShuffleOrder;
 import com.google.android.exoplayer2.util.Assertions;
 
 /** Abstract base class for the concatenation of one or more {@link Timeline}s. */
-/* package */ abstract class AbstractConcatenatedTimeline extends Timeline {
+public abstract class AbstractConcatenatedTimeline extends Timeline {
 
   private final int childCount;
   private final ShuffleOrder shuffleOrder;

library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -19,6 +19,7 @@ import android.os.Handler;
 import android.os.Message;
 import androidx.annotation.GuardedBy;
 import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.AbstractConcatenatedTimeline;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.ConcatenatingMediaSource.MediaSourceHolder;

library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.source;
 
 import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.AbstractConcatenatedTimeline;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.Player;