Bug 1177244 - Add in tools namespace. r=me

I removed it in a botched rebase and broke the build.

--HG--
extra : commitid : 7ZgYEHIYXFZ

mobile/android/base/resources/layout/tab_queue_prompt.xml

@@ -6,6 +6,7 @@
 
 <merge
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/tab_queue_container"
     android:layout_width="match_parent"
     android:layout_height="match_parent"