Set ToolBoxItemBits inside the controller

Don't rely on the toolbar:style attribute of the toolbar xml,
because it's not available after toolbar customization, or
when placing the button on a different toolbar.

See 99ace739828f9d79a2f9b04ef066b90d77f77bc4 for a similar fix.

Change-Id: Ia9485cafe111ba609fe802c984be1aa9db3a2ca9