Partialy revert "Make ExtractorMediaSource timeline dynamic until duration is set"

This change broke playback through playlists.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=176764830

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

@@ -327,11 +327,9 @@ public final class ExtractorMediaSource implements MediaSource, ExtractorMediaPe
   private void notifySourceInfoRefreshed(long durationUs, boolean isSeekable) {
     timelineDurationUs = durationUs;
     timelineIsSeekable = isSeekable;
-    // If the duration is currently unset, we expect to be able to update the window when its
-    // duration eventually becomes known.
-    boolean isDynamic = timelineDurationUs == C.TIME_UNSET;
+    // TODO: Make timeline dynamic until its duration is known. This is non-trivial. See b/69703223.
     sourceListener.onSourceInfoRefreshed(this,
-        new SinglePeriodTimeline(timelineDurationUs, timelineIsSeekable, isDynamic), null);
+        new SinglePeriodTimeline(timelineDurationUs, timelineIsSeekable, false), null);
   }
 
 }