Ticket #30021: 30021-2.patch

src/wp-includes/css/admin-bar.css

@@ -16 +16 @@
         -webkit-transition: none;
         transition: none;
         -webkit-font-smoothing: subpixel-antialiased; /* Prevent Safari from switching to standard antialiasing on hover */
+        -moz-osx-font-smoothing: auto; /* Prevent Firefox from displaying thin font when themes turn on font-smoothing */
 }
 
 .rtl #wpadminbar * {