Bug 1523703 - Disable discoverystream in test environment r=andreio

Differential Revision: https://phabricator.services.mozilla.com/D18755

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

testing/profiles/common/user.js

@@ -10,6 +10,8 @@ user_pref("browser.newtabpage.activity-stream.asrouter.providers.snippets", "[]"
 user_pref("browser.newtabpage.activity-stream.feeds.section.topstories", false);
 user_pref("browser.newtabpage.activity-stream.feeds.snippets", false);
 user_pref("browser.newtabpage.activity-stream.tippyTop.service.endpoint", "");
+user_pref("browser.newtabpage.activity-stream.discoverystream.config", "{\"enabled\": false}");
+
 // For Activity Stream firstrun page, use an empty string to avoid fetching.
 user_pref("browser.newtabpage.activity-stream.fxaccounts.endpoint", "");
 // Background thumbnails in particular cause grief, and disabling thumbnails