This implements a COM Server and returns objects implementing INotificationActivationCallback. This allows Firefox notifications to be acted upon even after the main process exits.
COM objects require a (normally static) CLSID in the registry to be identified by other apps. To prevent CLSID duplication between parallel installs and portable/development builds, this implementation inspects the registry when a COM object CLSID is requested, and returns an object if the CLSID's InprocServer32 key matches the path of the DLL.
Differential Revision: https://phabricator.services.mozilla.com/D149182
94c7867e54