android/testData/designer/included.xml

<?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:layout_gravity="center_horizontal"
    android:orientation="vertical"
    android:background="ffff0000"
    tools:showIn="@layout/includer">

    <TextView
        android:id="@+id/textView4"
        android:layout_width="500px"
        android:layout_height="80px"
        android:text="Included Layout"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="500px"
        android:layout_height="80px"
        android:text="This text is from the included layout" />
</LinearLayout>