We want to make sure the request is finished after clicking a button and
before visiting a different page, so we need to check the page has
changed.
Usually this shouldn't be a problem because most of our forms are sent
with regular HTTP requests instead of AJAX ones, so the `visit` method
wouldn't be called before the request is finished.
However, we're experiencing problems with certain version of
Chromedriver, and in general it's a good practice because we might send
forms using AJAX/Turbolinks in the future.
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