[6.5.3][modern] Ext.field.Date mousedown event params are wrong

[Grigoriy Mikhalkin]

In modern toolkit in Ext.field.Date, documentation says `mousedown` event listener should expect to receive following arguments:

* @param {Ext.field.Text} this This field.
* @param {Ext.event.Event} e.

But, in fact, receives only:

* @param {Ext.event.Event} e.

Link: http://docs.sencha.com/extjs/6.5.3/m...vent-mousedown