Bug 1579325 - Fix test failure, r=jlast.

Differential Revision: https://phabricator.services.mozilla.com/D45054

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

devtools/client/webreplay/mochitest/browser_dbg_rr_console_warp-03.js

@@ -9,6 +9,7 @@
 const BrowserTest = {
   gTestPath,
   ok,
+  is,
   registerCleanupFunction,
   waitForExplicitFinish,
   BrowserTestUtils,