Bug 1581753 - Improve one-off search button layout in narrow windows. r=mak

Differential Revision: https://phabricator.services.mozilla.com/D47270

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

browser/themes/shared/urlbar-autocomplete.inc.css

@@ -394,7 +394,10 @@
 }
 
 #urlbar .search-panel-one-offs {
-  padding-inline: 12px;
+  padding-inline-start: 12px;
+  /* Make sure we can fit at least three buttons horizontally. */
+  min-width: 120px;
+  box-sizing: content-box;
 }
 
 #urlbar .search-panel-header {