Bug 1403734 - Set border radius for customize mode footer buttons. r=Gijs

MozReview-Commit-ID: 2ZK56nGC5Jt

--HG--
extra : rebase_source : e7d0e037f5ff46bd5526aeeda0f99e10654afda1

browser/themes/shared/customizableui/customizeMode.inc.css

@@ -57,6 +57,7 @@
 
 .customizationmode-button {
   border: 1px solid #b1b1b1;
+  border-radius: 2px;
   background-color: #fcfcfd;
   -moz-appearance: none;
 }