This test case was failing on platforms where the default font
does not fit inside the default size of a fixed text control
(hard coded to be 12px high in UnoFixedTextControl's constructor)

 - Adjust the test case to explicitly set the text control's size
   to its preferred size.

 - Re-enable this checking on Mac OS X, where it had been disabled
   in 2013 due to this issue

Change-Id: I469a733f0a2719c60564d61c89bb64ab3ab622ba
Reviewed-on: https://gerrit.libreoffice.org/28961Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>