Bug 1534746 - Fix row fade-out direction for RTL. r=mak

Differential Revision: https://phabricator.services.mozilla.com/D23296

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

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

@@ -68,6 +68,10 @@
   mask-image: linear-gradient(to left, transparent, black 2em);
 }
 
+.urlbarView-row-inner[overflow]:-moz-locale-dir(rtl) {
+  mask-image: linear-gradient(to right, transparent, black 2em);
+}
+
 .urlbarView-row:hover {
   background: var(--arrowpanel-dimmed);
 }