I got WinCairo to compile and run without crashing using ACCELERATED_COMPOSITING. The poster circle example (https://www.webkit.org/blog-files/3d-transforms/poster-circle.html) runs the cpu, but doesn't draw anything, so I'm still missing something, but I'll start uploading my changes for review. Until now, AppleWin was the only port using ACCELERATED_COMPOSITING, so no effort was given to distinguish between the CA code and the ACCELERATED_COMPOSITING code. I've separated the two.
Created attachment 214982 [details] Patch
Comment on attachment 214982 [details] Patch r=me
Comment on attachment 214982 [details] Patch Clearing flags on attachment: 214982 Committed r157884: <http://trac.webkit.org/changeset/157884>
All reviewed patches have been landed. Closing bug.