Add final to boolean used within Runnable.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=176997767

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeSimpleExoPlayer.java

@@ -511,7 +511,7 @@ public class FakeSimpleExoPlayer extends SimpleExoPlayer {
       }
     }
 
-    private void stop(boolean quitPlaybackThread) {
+    private void stop(final boolean quitPlaybackThread) {
       playbackHandler.post(new Runnable() {
         @Override
         public void run () {