using JS_EvaluateUCScriptForPrincipals() in XULRunner 24

Hi all,

The SWT Browser's embedding of XULRunner uses 
JS_EvaluateUCScriptForPrincipals() to evaluate arbitrary JS code in the 
context of a loaded page.  This invocation is preceded by a 
nsIJSContextStack.Push() call to push the JSContext.

As of XULRunner 23 the nsIJSContextStack interface is gone, so I tried 
to just remove our Push() invocation (testing against XULRunner 24b2), 
and the JS_EvaluateUCScriptForPrincipals() call now crashes in 
ScriptSourceObject::create()'s invocation of cx->global(), because the 
JSContext's compartment() resolves to 0.

My question is, does the JSContext's compartment() == 0 indicate that 
not pushing the JSContext is likely the underlying problem?  And if so, 
what is the new way of doing this?  I notice within mozilla code the use 
of AutoPushJSContext, but this is not exported for use by embedders.

Or, if compartment() == 0 does not necessarily point at the JSContext 
not being pushed, does anything in the following sequence seem 
particularly wrong?

securityManager = serviceManager.getByContractID(ScriptSecurityManager)
principal = securityManager.getSystemPrincipal()
sgo = 
webBrowser.QI(nsIInterfaceRequestor).getInterface(nsIScriptGlobalObject)
sgo.EnsureScriptEnvironment()
scriptContext = sgo.getScriptContext()
jsContext = scriptContext.GetNativeContext()
jsPrincipals = principal.getJSPrincipals()
globalJSObject = sgo.GetGlobalJSObject()
JS_EvaluateUCScriptForPrincipals(jsContext, globalJSObject, 
jsPrincipals, ...)

Thank-you in advance,
Grant