The following tests need to be migrated off of URLRequestSlowDownloadJob:

DownloadNotificationTest.CancelDownload
DownloadNotificationTest.CloseNotificationAfterDownload
DownloadNotificationTest.CloseNotificationWhileDownloading
DownloadNotificationTest.DownloadCancelledByUserExternally
DownloadNotificationTest.DownloadFile
DownloadNotificationTest.DownloadMultipleFiles
DownloadNotificationTest.DownloadMultipleFilesOneByOne
DownloadNotificationTest.DownloadRemoved
DownloadNotificationTest.IncognitoDownloadFile
DownloadNotificationTest.InterruptDownload
DownloadNotificationTest.InterruptDownloadAfterClosingNotification
DownloadNotificationTest.SimultaneousIncognitoAndNormalDownloads
MultiProfileDownloadNotificationTest.DownloadMultipleFiles

I think net::test_server::ControllableHttpResponse can be used instead of URLRequestSlowDownloadJob. Apparently qinmin@ has done similar conversions for download tests.