After the previous patches, we no longer rely on the component manager
to incidentally start up XPConnect when we load the JS loader service
or to hold the JS component loader alive, so the do_GetService() call
for the JS loader in XPCOMInit.cpp can be removed. After that is done,
the JS loader is no longer used as an XPCOM component, so all of the
boilerplate for that can be removed.
Depends on D8757
Differential Revision: https://phabricator.services.mozilla.com/D8758
--HG--
extra : moz-landing-system : lando
9978e851df