code: function(event) {
        if(this.layer) {
           if(this.layer.focusedContainer && this.layer.focusedContainer != this) {
              this.layer.focusedContainer.removeFocus();
           }
           this.setFocus();
           this.layer.focusedContainer = this;
        }
     }
docs: Called when the user made a mouse down on the container and sets the focus to this container (only if within a Layer)
  @method onMouseDown