iFrame in Firefox hidden window with a contentWindow.history?

I'm trying to run a hosted script with content privileges in my Firefox extension. To do this, I create a content iframe in the hidden window pointed at a html file that pulls the script. This script requires开发者_高级运维 the 'history' be available, but the iframes created in the hidden window have no history for some reason.

Chromebug reports this for the iframe's contentWindow.history:

object does not support history (nsIDOMHistory)

And the script gives this error when its not available:

Error: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMHistory.length]

Any ideas?

It turns out that the hidden window's URL used to be about:blank, but this was apparently a security flaw, so it is now resource://gre/res/hiddenWindow.html (or resource://gre-resources/hiddenWindow.html on trunk) so it doesn't have the chrome privileges that a XUL browser element needs in order to be able to wire up its own session history, or even to access its own content document.

Even using a XUL iframe element you have to be careful since none of its properties work, again because it is running without chrome privileges. So you have to do stuff like iframeElement.boxObject.QueryInterface(Components.interfaces.nsIContainerBoxObject).docShell.QueryInterface(Components.interfaces.nsIInterfaceRequestor).getInterface(Components.interfaces.nsIDOMWindow) to retrieve its content window.

A <browser type="content"> will automatically wire up session history by default, while an <iframe type="content"> will not, but you could always wire it up yourself manually.

Don't forget to ensure that your element is created in the XUL namespace. I believe the hidden window is the about:blank HTML document except on the Mac.