Don't forget isSeekable in ExtractorMediaSource.

We currently forget whether a source is seekable at re-preparation. This was
implemented intentionally this way under the assumption that we really can't seek
until we have loaded the seek map again. However, seek operations are only
allowed after a media period is prepared. So there is no harm in remembering
whether a source is seekable.

This problem currently prevents reusing ClippingMediaSources with
ExtractorMediaSource and a non-zero start clip position.

Issue: #5351
PiperOrigin-RevId: 229169441

RELEASENOTES.md

@@ -9,6 +9,9 @@
 * Fix issue where sending callbacks for playlist changes may cause problems
   because of parallel player access
   ([#5240](https://github.com/google/ExoPlayer/issues/5240)).
+* Fix issue with reusing a `ClippingMediaSource` with an inner
+  `ExtractorMediaSource` and a non-zero start position
+  ([#5351](https://github.com/google/ExoPlayer/issues/5351)).
 
 ### 2.9.3 ###
 

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

@@ -370,7 +370,7 @@ public void prepareSourceInternal(
       boolean isTopLevelSource,
       @Nullable TransferListener mediaTransferListener) {
     transferListener = mediaTransferListener;
-    notifySourceInfoRefreshed(timelineDurationUs, /* isSeekable= */ false);
+    notifySourceInfoRefreshed(timelineDurationUs, timelineIsSeekable);
   }
 
   @Override