tst_QGuiApplication::quitOnLastWindowClosed() is flaky on Windows

 	call C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication\target_wrapper.bat  release\tst_qguiapplication.exe -o c:\Users\qt\work\testresults\tests\auto\gui\kernel\qguiapplication330945437,xml -o -,txt
 ********* Start testing of tst_QGuiApplication *********
 Config: Using QtTest library 5.8.1, Qt 5.8.1 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2013)
 PASS   : tst_QGuiApplication::initTestCase()
 PASS   : tst_QGuiApplication::palette()
 PASS   : tst_QGuiApplication::modalWindow()
 FAIL!  : tst_QGuiApplication::quitOnLastWindowClosed() 'spy2.count() > 15' returned FALSE. ()
 tst_qguiapplication.cpp(866) : failure location
 PASS   : tst_QGuiApplication::genericPluginsAndWindowSystemEvents()
 PASS   : tst_QGuiApplication::layoutDirection()
 jom: C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication\Makefile [release-check] Error 2
 
 agent:2017/02/22 15:12:52 build.go:200: Process finished with error: exit status 2
 agent:2017/02/22 15:12:52 build.go:152: Error reading from stdout/err: exit status 2
 agent:2017/02/22 15:13:12 build.go:270: [c:\users\qt\MSVC2013.bat jom check] 900 1200
 
 C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication>call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" amd64  
 
 	call C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication\target_wrapper.bat  release\tst_qguiapplication.exe quitOnLastWindowClosed
 ********* Start testing of tst_QGuiApplication *********
 Config: Using QtTest library 5.8.1, Qt 5.8.1 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2013)
 PASS   : tst_QGuiApplication::initTestCase()
 FAIL!  : tst_QGuiApplication::quitOnLastWindowClosed() 'spy2.count() > 15' returned FALSE. ()
 tst_qguiapplication.cpp(866) : failure location
 PASS   : tst_QGuiApplication::cleanupTestCase()
 Totals: 2 passed, 1 failed, 0 skipped, 0 blacklisted, 3084ms
 ********* Finished testing of tst_QGuiApplication *********
 jom: C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication\Makefile.Release [check] Error 1
 jom: C:\Users\qt\work\qt\qtbase\tests\auto\gui\kernel\qguiapplication\Makefile [release-check] Error 2
 
 agent:2017/02/22 15:13:17 build.go:200: Process finished with error: exit status 2
 agent:2017/02/22 15:13:17 agent.go:160: Test failed
 agent:2017/02/22 15:13:17 agent.go:117: ERROR building: exit status 2
 agent:2017/02/22 15:13:17 build.go:152: Error reading from stdout/err: exit status 2
 Build log: http://testresults.qt.io/logs/qt/qtbase/5a48f3d3d1aa43c6f75f5ba239e92da5a80ea630/WindowsWindows_8_1x86_64WindowsWindows_8_1x86_64MSVC2013qtci-windows-8-x86_64-7b67adDeveloperBuild_Release_BuildExamples/85d6b000f945a84bc84a4f01f53ac65bc05cbe86/testrun_1487763534/testlog.txt.gz
 Details: http://testresults.qt.io/coin/integration/qt/qtbase/tasks/1487763534
 Tested changes (refs/builds/qtci/5.8/1487763532):
   https://codereview.qt-project.org/#/q/d73f0bfa366b26551b8a8582400d0cd3fde454f9,n,z dockwidgets: recalculate the press position if the window resizes