gistfile1.js

    if (active) {
      if (this._currentDirection !== null) {
        active.set("buildDirection", this._currentDirection);
        this.buildOutChild(active);
      } else {
        this.removeChild(active);
      }
    }
    if (replacement) {
      if (this._currentDirection !== null) {
        replacement.set("buildDirection", this._currentDirection);
        this.buildInChild(replacement);
      } else {
        this.removeChild(replacement); /// this should be append child not remove child!!!!!
      }
    }