Comment 2 for bug 984794

StacktraceTop:
 ?? ()
 general_composite_rect (imp=0xc25dc0, info=<optimized out>) at ../../pixman/pixman-general.c:197
 pixman_image_composite32 (op=<optimized out>, src=<optimized out>, mask=<optimized out>, dest=<optimized out>, src_x=4, src_y=2, mask_x=0, mask_y=0, dest_x=4, dest_y=2, width=16, height=20) at ../../pixman/pixman.c:712
 _composite_spans (closure=<optimized out>, dst=<optimized out>, dst_format=<optimized out>, op=CAIRO_OPERATOR_OVER, pattern=<optimized out>, dst_x=4, dst_y=0, extents=0x7f344bfee620, clip_region=0x0) at /build/buildd/cairo-1.10.2/src/cairo-image-surface.c:3510
 _clip_and_composite (dst=0x7f344c007660, op=CAIRO_OPERATOR_OVER, src=0x7f344bfee730, draw_func=0x7f346e9066b0 <_composite_spans>, draw_closure=0x7f344bfedcf0, extents=0x7f344bfee600, clip=0x0) at /build/buildd/cairo-1.10.2/src/cairo-image-surface.c:2316