Comment 13 for bug 1231917

After a bit of more investigation, this actually seems to be a bug in the way Mir is using the hwcomposer interface (not using the 2 layers, and also with a different init/flags set).

The crash happens because it tries to use a pthread_mutex that is not initialized. From our current investigation nothing is calling/using this pthread_mutex before the crash, so it's probably due a different code path used with Mir.