Android/app/src/main/res/drawable/rounded_rectangle_dialog_secondary.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" >
    <solid android:color="@color/signal_background_dialog_secondary"/>
    <corners android:radius="30dp"/>
</shape>