I know it’s an old post, but you can try using Cards like so:
<android.support.v7.widget.CardView
android:layout_width="300dp"
android:layout_height="350dp"
android:layout_gravity="center_horizontal|center_vertical"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="20dp"
app:cardCornerRadius="12dp"
app:cardElevation="12dp">
<fragment
android:id="@+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.v7.widget.CardView>