Keep playback position advancing when all renderers are disabled.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123977520

library/src/main/java/com/google/android/exoplayer/ExoPlayerImplInternal.java

@@ -361,6 +361,8 @@ import java.util.concurrent.atomic.AtomicInteger;
       }
       updateBufferedPositionUs();
       source.continueBuffering(positionUs);
+    } else {
+      updatePositionUs();
     }
 
     boolean allRenderersEnded = true;