Bug 1222786 - make tab groups removal warning in tab groups UI more prominent, r=jaws

--HG--
extra : commitid : hfpDV5mia8
extra : rebase_source : ee48df3109a68b041b5be2782657729918111732
extra : amend_source : 69c4ca7dfd077d096ca972b77cd59a81d52784f6

browser/components/tabview/ui.js

@@ -1571,6 +1571,7 @@ var UI = {
     let banner = iQ("<div>")
       .text(notificationText)
       .addClass("banner")
+      .css({background: 'linear-gradient(#ffe13e, #ffc703)', color: 'rgba(0,0,0,0.95)'})
       .append(button)
       .appendTo("body");