While opening Communigate Pro web-interface, I have:
firefox: cairo-xlib-surface.c:832: _get_image_surface: Assertion `extents->y + extents->height <= surface->height' failed.

bisected to

a69335a84eb9225b477cc8c753470eb3805b852c is the first bad commit
commit a69335a84eb9225b477cc8c753470eb3805b852c
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Jul 22 00:36:03 2011 +0100

    API: map-to-image and create-similar-image
    
    A common requirement is the fast upload of pixel data. In order to
    allocate the most appropriate image buffer, we need knowledge of the
    destination. The most obvious example is that we could use a
    shared-memory region for the image to avoid the transfer cost of
    uploading the pixels to the X server. Similarly, gl, win32, quartz...
    
    The other side of the equation is that for manual modification of a
    remote surface, it would be more efficient if we can create a similar
    image to reduce the transfer costs. This strategy is already followed
    for the destination fallbacks and this merely exposes the same
    capability for the application fallbacks.
    
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

:040000 040000 de70606dccbd792e7dd4494fc1a0dd733bdd0f32 fb65e1f9201f914137d8c41999e4b0881b984ddf M	src
:040000 040000 e3bb5f9ad7ca033c0b38178695248b85113bff5b 07f5fd76bf3b851577be1dd01992009587c3b080 M	test
:040000 040000 f2e5de12ef56f51dc735ab656194815cd44f1bf1 589d880b314f7957ce7dea77a150c9050895ba89 M	util