res: Allow gallery to be navigated using only controller.

res/layout/gallery_item_adapter.xml

@@ -1,5 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:background="@android:drawable/list_selector_background"
+    android:focusable="true"
     android:id="@+id/galleryItem"
     android:layout_width="match_parent"
     android:layout_height="match_parent"