[cairo] Further cairo GL/GLES2 work

[Alexandros Frantzis]

Hi all!

As the current (Linaro) development cycle comes to end, I have started
thinking about additional work that can be done to improve the cairo
GL/GLES2 backend. Depending on the priority of other tasks, I will
probably have some time to spend on further cairo GL/GLES2
improvements/fixes and I would like to focus more on performance
(functionality/correctness will still remain important of course).

Although I will perform some profiling on my own, I am sure some people
(Chris,Eric ?) already have good ideas on improving cairo-gl
performance. If you think something is worth doing (or even just
investigating) please contact me, so I can include it in my planning.

Thanks,
Alexandros