We have a button in a Lightning component as follows:
<ui:button label="Associate" press="{!c.associateUsages}"></ui:button>

The controller function looks like this:
    associateUsages: function (component, event, helper) {
        var recordId = component.get("v.recordId");
        var url = '/apex/OpportunityCustomerUsages?id=' + recordId;
        window.open(url, '_self');
    }

This works except that the VF page that is invoked is standalone and doesn't get decorated with the Lightning UI wrapper. And we'd like for it to look like a Lightning page with the UI wrapper. Any suggestions? Thanks in advance.