There are two places using DBService during a page load at startup:
1. nsChannelClassifier::Start, used by Phishing Protection
2. AsyncChannelClassifier::CheckChannel, used by Tracking Protection
Tracking protection checks happen before establishing a network connection, so it happens
prior to phishing protection checkes. When we load a page at
startup, ::CheckChannel API is called, but DBService is not yet created.
This patch fixes this issue by creating a DBService instance when
::GetWorker API is called without a DBService instance.
Differential Revision: https://phabricator.services.mozilla.com/D55248
2f65764a31