ScaledFont: Add the missing get_extents() method implementation.
ScaledFont: Add the missing get_extents() method implementation.

Bug #53981 (cheshirekow)

johne53/MB3Cairomm,johne53/MB3Cairomm,johne53/MB3Cairomm,Mixaill/cmake.cairomm,Mixaill/cmake.cairomm,johne53/MB3Cairomm