Add uses-feature for live wallpaper sample.

Change-Id: I766d72ea79e8ef9530b2c485376a3429b530a00f

samples/CubeLiveWallpaper/AndroidManifest.xml

diff --git a/samples/CubeLiveWallpaper/AndroidManifest.xml b/samples/CubeLiveWallpaper/AndroidManifest.xml
index 1c6507b..b7bb876 100644
--- a/samples/CubeLiveWallpaper/AndroidManifest.xml
+++ b/samples/CubeLiveWallpaper/AndroidManifest.xml
@@ -21,6 +21,8 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.android.livecubes">
 
+    <uses-feature android:name="android.software.live_wallpaper" />
+
     <application
         android:label="@string/wallpapers"
         android:icon="@drawable/ic_launcher_wallpaper">