comctl32/tab: Fix DRAWITEMSTRUCT filling when extra item data of a custom size is used (try2)

[testbot at testbot.winehq.org]

Hi,

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?
Full results can be found at
http://testbot.winehq.org/JobDetails.pl?Key=5580

Your paranoid android.


=== W98SE (32 bit tab) ===
tab.c:1354: Test failed: got 0xdedede, expected 0xdededede

=== W7PROX64 (64 bit tab) ===
tab.c:1354: Test failed: got 0xdededede, expected 0xdededede