Bug 1607448 - Properly wait for messages to be evaluated in browser_webconsole_reverse_search_keyboard_navigation. r=Honza.

Without this patch, sometimes the result messages were
added as the toolbox was closing, which emits very long
messages from the ignore middleware, making parsing logs
almost impossible.

Differential Revision: https://phabricator.services.mozilla.com/D58950

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

devtools/client/webconsole/test/browser/browser_webconsole_reverse_search_keyboard_navigation.js

@@ -20,7 +20,7 @@ add_task(async function() {
     `Dog = "Snoopy"`,
   ];
 
-  const onLastMessage = waitForMessage(hud, `"Snoopy"`);
+  const onLastMessage = waitForMessage(hud, `"Snoopy"`, ".result");
   for (const input of jstermHistory) {
     execute(hud, input);
   }