gecko-dev/mobile/android/base/resources/xml/gecko_appwidget_info.xml

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
                    android:minWidth="270dp"
                    android:minHeight="54dp"
                    android:initialLayout="@layout/gecko_appwidget"
                    android:resizeMode="horizontal"/>