DataTable: changing page size doesn't properly update the current page number

[mkrause]

To reproduce:

1. Take a DataTableEager with a lot of pages, for example this story.
2. Go to a subsequent page (e.g. page 3)
3. Increase the page size (e.g. 50 instead of 10)
4. Notice that the page size has increased, but the page number still reflects the old state (e.g. if it was page 3 before it's still on page 3 after)