Most browsers have `self` as the `window` object, our test browser
doesn't have the `self` variable, recent update in form-data
form-data/form-data@f64a4c3 switched to use `self`, this fix adds
`self` reference back so it is aligned with browser behavior
Add a simple implementation of getRandomValues to the browser context
to get rid of the following warning:
[SECURITY] node-uuid: crypto not usable, falling back to insecure
Math.random()
David Cheung
Miroslav Bajtoš
Ryan Graham
Raymond Feng
Krishna Raman