While running your changed tests on Windows, I think I found new failures. Being a bot and all I'm not very good at pattern recognition, so I might be wrong, but could you please double-check?
=== w7pro64 (64 bit taskdialog) === 0824:taskdialog: unhandled exception c0000005 at 00000000004620FE
Yes, this is indeed an issue, although I can't reproduce it on my machine. But the whole patch could probably need improvement. The reason I added it in the first place, is that some messages can only be sent after the first are processes, else one of them is basically ignored. Just try to remove the "SEND_SYNCRONIZED" from the mssage lists, and the tests are gonna fail. On both windows and wine, and I didn't find a better way to fix that issue yet.
Does someone have an idea for that problem?
Regards, Fabian Maurer