For #2324 - Adds a drawable with the proper border radius

app/src/main/res/drawable/dialog_button_background.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<shape xmlns:android="http://schemas.android.com/apk/res/android">
+    <corners android:radius="8dp"/>
+    <solid android:color="?inset" />
+</shape>

app/src/main/res/values/styles.xml

@@ -169,7 +169,7 @@
     </style>
 
     <style name="SitePermissionPrimaryButton" parent="SitePermissionButton">
-        <item name="android:background">@drawable/button_background</item>
+        <item name="android:background">@drawable/dialog_button_background</item>
         <item name="android:textColor">?contrastText</item>
         <item name="android:backgroundTint">?accent</item>
     </style>