Replace IndexOutOfBounds Exception for BehindLiveWindowException

This is a problem when two invocations of getNextChunk that retrieve
chunks (i.e. not playlists) occur too apart in time. In that case
the last loaded chunk has a media sequence that is behind the current
playlist.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=136501291

library/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java

@@ -440,6 +440,10 @@ import java.util.Locale;
     }
     }
     HlsMediaPlaylist oldMediaPlaylist = variantPlaylists[oldVariantIndex];
     HlsMediaPlaylist oldMediaPlaylist = variantPlaylists[oldVariantIndex];
     HlsMediaPlaylist newMediaPlaylist = variantPlaylists[newVariantIndex];
     HlsMediaPlaylist newMediaPlaylist = variantPlaylists[newVariantIndex];
+    if (previousChunkIndex < oldMediaPlaylist.mediaSequence) {
+      // We have fallen behind the live window.
+      return newMediaPlaylist.mediaSequence - 1;
+    }
     double offsetToLiveInstantSecs = 0;
     double offsetToLiveInstantSecs = 0;
     for (int i = previousChunkIndex - oldMediaPlaylist.mediaSequence;
     for (int i = previousChunkIndex - oldMediaPlaylist.mediaSequence;
          i < oldMediaPlaylist.segments.size(); i++) {
          i < oldMediaPlaylist.segments.size(); i++) {