After this patch landed, we will have 3 cases:
1. For providers are not "test", for example, google, google4, mozilla ... etc
backoff CANNOT be disabled.
2. For "test" provider, if preference "browser.safebrowsing.provider.test.disableBackoff" is ON
backoff is disabled.
3. For "test" provider, if preference "browser.safebrowsing.provider.test.disableBackoff" is Off
backoff is NOT disabled.
So if your testcase will use listmanager or hashcompleter, you should try to use "test" provider
if possible, otherwise testcase may encounter intermittent failure due to backoff.
MozReview-Commit-ID: 3BDxs0ARyQM
47c5b9727a