[cairo] Image-Data upload using SHM

[Clemens Eisserer]

Hi,

I did some profiling of Firefox's html5 video element which uses
cairo, and the low performance I observed seems to be caused by not
using XShmPutImage for uploading video-data.
Instead, XPutImage is used - with xcb's 16kb buffer this results in
about ~25k cs/s, slowing my machine down to a crawl.

Does cairo support using the XSHM extensions, or are there patches available?

Thanks you in advance, Clemens