When a page does many ajax requests, the list of done ajax requests can get very long. This uses memory and slows down the page. To avoid this I propose a configurable maximum number of ajax requests shown in the debug toolbar. Older ones would be removed from the list (and ... would be at the end). We can still find them in the profiler log.

example config

web_profiler:
    # maximal number of ajax requests to show in debug toolbar, null is unlimited
    max_ajax_requests_in_toolbar: null