Enable full data download for wordcloud

The `load more data` in the wordcloud does _something_ (shows a loading spinner for a while, then finishes), but perhaps the loaded data is not actually used. In any case, the frequency table is not updated when loading more data. The wordcloud picture is re-drawn, but I don't think the data changes. (It has a random component, so it's hard to see.)

Start by tracing the wordcloud's “load more data” action and the code that updates the frequency table. Reproduce the loading behavior, then verify that loading more data changes both the frequency table and the wordcloud output; done means the additional data is actually used.

Written by the indexing model from the issue text.