Bug 1798683 - Make browser_unified_extensions_overflowable_toolbar.js more resilient by using a constant set of extension IDs. r=willdurand,extension-reviewers

For reasons that I don't fully understand, this appears to make the test pass more reliably on all platforms.

Differential Revision: https://phabricator.services.mozilla.com/D162577

browser/components/extensions/test/browser/browser.ini

@@ -428,4 +428,3 @@ https_first_disabled = true
 [browser_unified_extensions_doorhangers.js]
 [browser_unified_extensions_overflowable_toolbar.js]
 tags = overflowable-toolbar
-skip-if = true # Bug 1798683

browser/components/extensions/test/browser/browser_unified_extensions_overflowable_toolbar.js

@@ -179,6 +179,9 @@ async function withWindowOverflowed(win, taskFn) {
       browser_action: {
         default_area: "navbar",
       },
+      browser_specific_settings: {
+        gecko: { id: `unified-extensions-overflowable-toolbar@ext-${i}` },
+      },
     });
   }