'query: the main query to retrieve the pass rate information.  The first
column contains the hostnames of all the machines that satisfied the
global filter. The second column (titled \'total\') contains the total
number of tests that ran on that machine and satisfied the global
filter. The third column (titled \'good\') contains the number of
those tests that passed on that machine.
filter_string: filter to apply to the common global filter to show the
Table View drilldown of a histogram bucket
interval: interval for each bucket. E.g., 10 means that buckets should
be 0-10%, 10%-20%, ...'

def __init__(self, query, filter_string, interval, drilldown_callback):

    self.query = query
    self.filter_string = filter_string
    self.interval = interval
    self.drilldown_callback = drilldown_callback
