lib/Ext/util/Droppable.js
function() {
        if (!this.mgr) {
            this.mgr = Ext.util.Observable.observe(Ext.util.Draggable);
        }
        this.mgr.on({
            dragstart: this.onDragStart,
            scope: this
        });
        this.disabled = false;
    }
function() {
        if (!this.mgr) {
            this.mgr = Ext.util.Observable.observe(Ext.util.Draggable);
        }
        this.mgr.on({
            dragstart: this.onDragStart,
            scope: this
        });
        this.disabled = false;
    }
Enable the Droppable target.
This is invoked immediately after constructing a Droppable if the
disabled parameter is NOT set to true.