Compiz leaks Windows resources

Steps to reproduce:
1. Run "xrestop" and check how many Windows Compiz uses
2. Run large number of other (3D) applications
3. Redo 1)

Actual outcome:
- X Windows references by Compiz constantly increases although all run programs have been closed

Expected outcome:
- No leakage, of X resources or other things

This happens with latest Compiz version both on Ubuntu 14.04 and Ubuntu 14.10.

How did I notice this:
- Running many application causes random OOM killings with recent (end of January intel-drm-next) kernel built from sources, on a BDW machine
- When reproducing the issue, I first thought this a kernel leakage because according to "slabtop", kernel vm_page_struct object numbers were increasing
- From kernel backtraces on OOM-kill I could see that it was triggered by graphics memory allocation failure so I checked from sysfs whether DRI/GEM objects were leaking, but that didn't show anything leaking
- However, with "xrestop" I could see that Compiz was leaking Windows resources. I think that explains the vm_page_struct object count increase on the kernel side, i.e. that was just result of Compiz leakage on user-space