Bug 39970

In the following code snippet, cairo_fill_extents incorrectly returns zero (empty) rectangle.
This affects version 1.10.2 (in 1.8.10, the result is correct for this specific case).

cairo_new_path( &Cairo );
cairo_move_to( &Cairo, 4, 8 );
cairo_line_to( &Cairo, 6, 8 );
cairo_line_to( &Cairo, 6, 7 );
cairo_fill_extents( &Cairo, &x1, &y1, &x2, &y2 );