Use fitsSystemWindows for better demoing.

Change-Id: I3b9e5068401e0ac1cd1d631434fe1514e8996ee3
diff --git a/samples/ApiDemos/res/layout/overscan.xml b/samples/ApiDemos/res/layout/overscan.xml
index a0329b0..6a5304a 100644
--- a/samples/ApiDemos/res/layout/overscan.xml
+++ b/samples/ApiDemos/res/layout/overscan.xml
@@ -34,6 +34,7 @@
         android:background="#60000000"
         android:padding="8dp"
         android:orientation="vertical"
+        android:fitsSystemWindows="true"
         >
         <LinearLayout
             android:layout_width="match_parent"