We are now ready to bring back the on demand accelerated compositing mode with the threaded compositor. Unfortunately, having AC always enabled brought a lot of issues for many people. Not only it requires a lot more memory but also caused rendering issues (or even nothing rendered at all) with some graphics drivers. People started to use WEBKIT_DISABLE_COMPOSITING_MODE as a workaround, but that was not expected to be used by users. So, entering/leaving AC when required by web contents is not actually the solution but a huge improvement for many people. If we are eventually ready to force AC mode again, we'll change this again. Note that we still have WEBKIT_DISABLE_COMPOSITING_MODE, but now also WEBKIT_FORCE_COMPOSITING_MODE for testing and debugging.
Created attachment 299917 [details]
Committed r211277: <http://trac.webkit.org/changeset/211277>