overlay not working with Maps

Created by: quentin23soleil

The overlay attribute set to false or true doesn't change a thing with a Map as the main content.

Here's the main content:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:showIn="@layout/activity_home">

    <include
        android:id="@+id/toolbar"
        layout="@layout/toolbar" />

    <RelativeLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <fragment
            android:id="@+id/map"
            android:name="com.google.android.gms.maps.SupportMapFragment"
            xmlns:map="http://schemas.android.com/apk/res-auto"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            map:mapType="normal"
            map:uiCompass="true" />

        <ImageView
            android:id="@+id/splash_screen_hack"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_centerInParent="true"
            android:background="@color/primary"
            android:scaleType="centerInside"
            android:src="@drawable/bg_splashscreen"
            android:visibility="visible" />
    </RelativeLayout>
</LinearLayout>