protected void replaceChildren(List<T> values, int start, SafeHtml html) {
        Element newChildren = convertToElements(html);
        replaceChildren(this, getChildContainer(), newChildren, start, html);
    }
Convert the specified HTML into DOM elements and replace the existing
elements starting at the specified index. If the number of children
specified exceeds the existing number of children, the remaining children
should be appended.

@param values the values of the new children
@param start the start index to be replaced, relative to the page start
@param html the html to render, or null if
         {@link #renderRowValues(SafeHtmlBuilder, List, int, SelectionModel)}
         throws an {@link UnsupportedOperationException}
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/AbstractHasData.java