Don't return a TrackStream from TrackRenderer.disable.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125659817

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

@@ -878,9 +878,8 @@ import java.util.ArrayList;
               rendererMediaClockSource = null;
             }
             ensureStopped(renderer);
-            // TODO[playlists]: Consider using TrackStreams from the timeline source instead of
-            // returning a TrackStream from TrackRenderer.disable.
-            oldStreams.add(renderer.disable());
+            renderer.disable();
+            oldStreams.add(playingSource.trackStreams[i]);
           }
           if (newSelection != null) {
             newSelections.add(newSelection);

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

@@ -314,14 +314,12 @@ public abstract class TrackRenderer implements ExoPlayerComponent {
   /**
    * Disable the renderer.
    */
-  /* package */ final TrackStream disable() {
+  /* package */ final void disable() {
     Assertions.checkState(state == STATE_ENABLED);
     state = STATE_DISABLED;
     onDisabled();
-    TrackStream trackStream = stream;
     stream = null;
     streamIsFinal = false;
-    return trackStream;
   }
 
   /**