GeckoFx separate cookies for each Control

I want to create a new GeckoWebBrowser control but with a separate set of cookies for each control.

I tried with this code but it gives me an error:

<ContractID(TestCookieServiceFactory.ContractID)>
Public Class TestCookieServiceFactory
    Inherits GenericOneClassNsFactory(Of TestCookieServiceFactory, TestCookieService)

    Public Const ContractID As String = "@mozilla.org/cookieService;1"
End Class

Public Class TestCookieService
    Inherits nsICookieConsts
End Class

Public Sub Main()
    Xpcom.Initialize("Firefox")

    Dim existingFactoryDetails = TestCookieServiceFactory.Unregister()
    TestCookieServiceFactory.Register()

    Dim browser = New Gecko.GeckoWebBrowser
    browser.Navigate("http://www.twitter.com")
End Sub

Error message:

An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in Geckofx-Core.dll

Additional information: Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))