Word 2016 queries a lot of font glyph bounding boxes and bitmaps with translation matrices. The
result of these queries is not cached because the transform matrix is not the identity matrix.
However, the translation offsets don't affect FreeType font operations at all, which can be
verified in ft_matrix_from_dwrite_matrix() called by get_glyph_transform(). So these results with
translation matrices can be cached as well. With this patch, Word 2016 stuttering is reduced
significantly.