TestWebChannel::testAsyncObject() fails randomly

call C:\Users\qt\work\qt\qtwebchannel\tests\auto\webchannel\target_wrapper.bat  release\tst_webchannel.exe testAsyncObject
 ********* Start testing of TestWebChannel *********
 Config: Using QtTest library 5.7.1, Qt 5.7.1 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2013)
 PASS   : TestWebChannel::initTestCase()
 FAIL!  : TestWebChannel::testAsyncObject() 'spy.wait()' returned FALSE. ()
 tst_webchannel.cpp(764) : failure location
 QWARN  : TestWebChannel::testAsyncObject() QThread: Destroyed while thread is still running
 PASS   : TestWebChannel::cleanupTestCase()
 Totals: 2 passed, 1 failed, 0 skipped, 0 blacklisted, 5017ms
 ********* Finished testing of TestWebChannel *********
 jom: C:\Users\qt\work\qt\qtwebchannel\tests\auto\webchannel\Makefile.Release [check] Error 1
 jom: C:\Users\qt\work\qt\qtwebchannel\tests\auto\webchannel\Makefile [release-check] Error 2
 
 agent:2016/10/31 12:22:03 build.go:200: Process finished with error: exit status 2
 agent:2016/10/31 12:22:03 agent.go:160: Test failed
 agent:2016/10/31 12:22:03 agent.go:117: ERROR building: exit status 2
 agent:2016/10/31 12:22:03 build.go:152: Error reading from stdout/err: exit status 2

 Build log: http://testresults.qt.io/logs/qt/qtwebchannel/be24afec9f39c584abff83888e842c25abbbddbb/WindowsWindows_8_1x86_64WindowsWindows_8_1x86_64MSVC2013qtci-windows-8-x86_64-b40ec6DebugAndRelease_Release_OpenGLDynamic/a19f8bb908f54c5022d16e1a4485ad8760f7d374/testrun_1477908301/testlog.txt.gz

 Details: http://testresults.qt.io/coin/integration/qt/qt5/tasks/1477908301

 Tested changes (refs/builds/qtci/5.7.1/1477908301):
   https://codereview.qt-project.org/#/q/4b9a14057a4949399719d088c6bee115f129aca2,n,z Update submodules on '5.7.1' in qt5