Start editing the specified grid at the specified position.
@param {Ext.data.Model} record The Store data record which backs the row to be edited.
@param {Ext.data.Model} columnHeader The Column object defining the column to be edited.
function(record, columnHeader) {
        var me = this,
            grid = me.editingPlugin.grid,
            store = grid.store,
            view = grid.getView(),
            context = me.context = Ext.apply(me.editingPlugin.context, {
                view: view,
                store: store
            });

        if (!me.rendered) {
            me.render(view.el);
        }
        // make sure our row is selected before editing
        context.grid.getSelectionModel().select(record);

        // Reload the record data
        me.loadRecord(record);

        if (!me.isVisible()) {
            me.show();
        }
        me.reposition({
            callback: this.focusContextCell
        });
    }