[lmi] "'SetFocus' failed" in automated GUI test

[Greg Chicares]

To reproduce:
  cd /opt/lmi/bin
  ./wx_test.exe --data_path=/opt/lmi/data --distribution >eraseme 2>&1
Symptom: output file begins:

In file ../src/msw/window.cpp at line 558: 'SetFocus' failed with error 
0x00000057 (the parameter is incorrect.).
In file ../src/msw/window.cpp at line 558: 'SetFocus' failed with error 
0x00000057 (the parameter is incorrect.).
NOTE: starting the test suite
about_dialog_version: started
About dialog version string is "20160809T1255Z".

where the first two lines are unexpected.

I cannot reproduce this either with msw-xp in a VM or with 'wine' in
my cross-building chroot. However, Kim observes it, reproducibly, in
native msw-7. She's certain that she is not touching the keyboard or
mouse during the test. She does NOT observe the anomaly if she adds
'--ash_nazg' to the command line.

I'm trying to imagine how this can occur. It looks like it must be
happening here:

void SkeletonTest::RunTheTests()
{
    wxWindow* const mainWin = GetTopWindow();
[Exit if that is NULL...]

    // Close any initially opened dialogs (e.g. "About" dialog shown unless a
    // special command line option is specified).
[The anomaly is not seen with '--ash_nazg', which suppresses that
"About" dialog...]

    mainWin->SetFocus();
    wxPuts("NOTE: starting the test suite");
[It's plausible to guess that this is the failing SetFocus() call.
But 'mainWin' was already tested for validity. Might the "About"
dialog be what GetTopWindow() chooses? only with msw7, not xp?]