docs: public GVRAnimation setOnFinish(GVROnFinish callback) {
          mOnFinish = callback;
  
          // Do the instance-of test at set-time, not at use-time
          mOnRepeat = callback instanceof GVROnRepeat ? (GVROnRepeat) callback
                  : null;
          if (mOnRepeat != null) {
              mRepeatCount = -1; // loop until iterate() returns false
          }
          return this;
      }