Likely a missing initial setNPWindow
Landed in r65067
Revision r65067 cherry-picked into qtwebkit-2.0 with commit 19b5607b7492a368d026d1f45253bbfd38dbd1ee
Revision r65067 cherry-picked into qtwebkit-2.1 with commit 1ca20156e02512399ffa9bdb15e41573f885e450