protected String getRowKeyFromConverter(T object) {
        FacesContext context = FacesContext.getCurrentInstance();
        return rowKeyConverter.getAsString(context, UIComponent.getCurrentComponent(context), object);
    }
Recalculates <code>first</code>, see #1921.
Also see: {@link org.primefaces.component.api.UIPageableData#calculateFirst()}

@param first the <code>first</code> param from the {@link #load(int, int, java.util.Map, java.util.Map)} method.
@param pageSize the <code>pageSize</code> param from the {@link #load(int, int, java.util.Map, java.util.Map)} method.
@param rowCount the new <code>rowCount</code>.
@return the recalculated <code>first</code>.
primefaces/src/main/java/org/primefaces/model/LazyDataModel.java