Can not set Http interface when invoked from webworker

[zeroX-tj]

We've been trying to get the User-Agent show up at the error report in Sentry. https://forum.sentry.io/t/raven-js-angular-2-unknown-browser-device/925

We run our code in a webworker which does not have a document but does have a navigator available. Unfortunatly _getHttpData returns too soon to set the headers because of the check on hasDocument and location.

It would be nice if at least the user-agent could be set.