[Bug 51078] New: mshtml:events hangs on Windows 10 1709

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51078

Bug ID: 51078
           Summary: mshtml:events hangs on Windows 10 1709
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mshtml
          Assignee: [e-mail]
          Reporter: [e-mail]

Created attachment 69941
  --> https://bugs.winehq.org/attachment.cgi?id=69941
Patch to more reliably reproduce the hang

mshtml:events sometimes hangs on Windows 10 1709:

http://winetest.dolphin/data/patterns.html#mshtml:events

For some reason this only happens on Windows 1709 (the reports say this is
mshtml 11.0.16299.309).

The test proceeds all the way to the end but then does not exit because the
mshtml component still has threads running:
  VSyncHelper
  Internet Explorer_Hidden
  MSCTFIME UI

Commenting out the test_focus() run gets rid of the hangs.
Also running the test with WINETEST_INTERACTIVE=1 greatly increases the
probability of getting a hang. I attached a patch that does that and can be
used to reproduce the hang on the TestBot's w1064v1709 VM.

So this is clearly related to focus.