AT-SPI2 application accessible does not send object:children-changed notifications

On AT-SPI2, when a top-level window is created, Qt adds the window to its application accessible, but it does not send an object:children-changed notification. Similarly, it does not send notifications when a top-level window is destroyed.

To observe this in Accerciser:

• Start a Qt application.
• Expand the application in Accerciser.
• Create a new window in the existing application such as a Preferences window.
• The new window does not immediately appear in Accerciser, but it does appear with a refresh.

This can also be observed using the "Event Monitor" feature of Accerciser.