tst_qquickwidget::enterLeave is flaky on Windows

: **********************************************************************
: ** Visual Studio 2017 Developer Command Prompt v15.4.0
: ** Copyright (c) 2017 Microsoft Corporation
: **********************************************************************
: [vcvarsall.bat] Environment initialized for: 'x64_x86'
:
: jom 1.1.2 - empower your cores
:
: 	C:\Utils\Jom\jom.exe -f Makefile.Release check
: 	call C:\Users\qt\work\qt\qtdeclarative\tests\auto\quickwidgets\qquickwidget\target_wrapper.bat  release\tst_qquickwidget.exe -o C:\Users\qt\work\testresults\tests\auto\quickwidgets\qquickwidget000347530,xml -o -,txt
: ********* Start testing of tst_qquickwidget *********
: Config: Using QtTest library 5.12.0, Qt 5.12.0 (i386-little_endian-ilp32 shared (dynamic) release build; by MSVC 2017)
: PASS   : tst_qquickwidget::initTestCase()
: PASS   : tst_qquickwidget::showHide()
: PASS   : tst_qquickwidget::reparentAfterShow()
: PASS   : tst_qquickwidget::changeGeometry()
: PASS   : tst_qquickwidget::resizemodeitem()
: PASS   : tst_qquickwidget::layoutSizeChange()
: PASS   : tst_qquickwidget::errors()
: PASS   : tst_qquickwidget::engine()
: PASS   : tst_qquickwidget::readback()
: PASS   : tst_qquickwidget::renderingSignals()
: PASS   : tst_qquickwidget::grab()
: PASS   : tst_qquickwidget::grabBeforeShow()
: PASS   : tst_qquickwidget::reparentToNewWindow()
: PASS   : tst_qquickwidget::nullEngine()
: PASS   : tst_qquickwidget::keyEvents()
: PASS   : tst_qquickwidget::shortcuts()
: FAIL!  : tst_qquickwidget::enterLeave() '(rootItem->property("hasMouse").toBool())' returned FALSE. ()
: tst_qquickwidget.cpp(548) : failure location
: PASS   : tst_qquickwidget::mouseEventWindowPos()
: PASS   : tst_qquickwidget::synthMouseFromTouch(no synth, accept)
: PASS   : tst_qquickwidget::synthMouseFromTouch(no synth, don't accept)
: PASS   : tst_qquickwidget::synthMouseFromTouch(synth and accept)
: PASS   : tst_qquickwidget::synthMouseFromTouch(synth, don't accept)
: PASS   : tst_qquickwidget::tabKey()
: PASS   : tst_qquickwidget::cleanupTestCase()
: Totals: 23 passed, 1 failed, 0 skipped, 0 blacklisted, 19022ms