Bug 1480815 - Define fxa autoconfig pref by default. r=markh

Differential Revision: https://phabricator.services.mozilla.com/D2727

--HG--
extra : moz-landing-system : lando

browser/app/profile/firefox.js

@@ -1377,6 +1377,12 @@ pref("identity.fxaccounts.remote.oauth.uri", "https://oauth.accounts.firefox.com
 // Token server used by the FxA Sync identity.
 pref("identity.sync.tokenserver.uri", "https://token.services.mozilla.com/1.0/sync/1.5");
 
+// Auto-config URL for FxA self-hosters, makes an HTTP request to
+// [identity.fxaccounts.autoconfig.uri]/.well-known/fxa-client-configuration
+// This is now the prefered way of pointing to a custom FxA server, instead
+// of making changes to "identity.fxaccounts.*.uri".
+pref("identity.fxaccounts.autoconfig.uri", "");
+
 // URLs for promo links to mobile browsers. Note that consumers are expected to
 // append a value for utm_campaign.
 pref("identity.mobilepromo.android", "https://www.mozilla.org/firefox/android/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=");