Prevent Firefox from showing an extra dotted border on focused buttons

Author: ry5n

UNRELEASED.md

@@ -17,6 +17,7 @@ Use [the changelog guidelines](https://git.io/polaris-changelog-guidelines) to f
 ### Enhancements
 
 - Made the `action` prop optional on `EmptyState` ([#1583](https://github.com/Shopify/polaris-react/pull/1583))
+- Prevented Firefox from showing an extra dotted border on focused buttons ([#1409](https://github.com/Shopify/polaris-react/pull/1409))
 
 ### Bug fixes
 

src/styles/global/elements.scss

@@ -50,3 +50,10 @@ p {
   font-size: 1em;
   font-weight: 400;
 }
+
+button::-moz-focus-inner,
+[type='button']::-moz-focus-inner,
+[type='reset']::-moz-focus-inner,
+[type='submit']::-moz-focus-inner {
+  border-style: none;
+}