LifeSpanHandler_DoClose
Called when a browser has received a request to close. If no OS window exists (window rendering disabled) returning false will cause the browser object to be destroyed immediately. Return true if the browser is parented to another window and that other window needs to receive close notification via some non-standard technique.
Return
False to send an OS close notification to the browser window's top-level owner.
Parameters
bid
The browser generating the event.