Stop using private resources

- call_background.xml points to one of private resource, but the method
  relying on the xml isn't used any more. Let's remove the entire
  method.
- use local version of action_menu_overflow_description

Bug: 6063210
Change-Id: I9ea6788ca4232492a8c62a8aa8460159314abee4
diff --git a/res/layout/dialpad_fragment.xml b/res/layout/dialpad_fragment.xml
index df13372..a95e4cb 100644
--- a/res/layout/dialpad_fragment.xml
+++ b/res/layout/dialpad_fragment.xml
@@ -98,7 +98,7 @@
             android:layout_height="?android:attr/actionBarSize"
             android:layout_gravity="bottom|center_horizontal"
             android:src="@drawable/ic_menu_overflow"
-            android:contentDescription="@*android:string/action_menu_overflow_description"
+            android:contentDescription="@string/action_menu_overflow_description"
             android:nextFocusLeft="@id/digits"
             android:background="?android:attr/selectableItemBackground"/>
     </LinearLayout>