declare namespace Ext {
    export namespace grid {
        export namespace header {
            export interface DropZoneConfig {
                containerScroll?: boolean;
                ddGroup?: string;
                dropAllowed?: string;
                dropNotAllowed?: string;
                overClass?: string;
            }

            export class DropZone extends Ext.dd.DropZone  {
            }
        }
    }
}