UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36

Steps to reproduce the problem:
1. Type the following in the developer console:

new Request('https://www.google.com', {method: 'POST', body: 'hi'}).body

2. Observe that the result is 'undefined'

What is the expected behavior?
Request is supposed to implement the Body mixin, so Requests with bodies should return a ReadableStream for the `body` property.

Relevant links:

https://fetch.spec.whatwg.org/#dom-body-body

https://developer.mozilla.org/en-US/docs/Web/API/Request

What went wrong?
The `body` property was undefined – among other things this makes it impossible to determine if a Request has a `body`, unless you use one of the other Body mixin methods which require actually reading the body and thus making the Request useless – unless you clone it beforehand.

Did this work before? N/A 

Does this work in other browsers? No
 Firefox exhibits the same behaviour: https://bugzilla.mozilla.org/show_bug.cgi?id=1514883

Chrome version: 70.0.3538.110  Channel: n/a
OS Version: OS X 10.14.2
Flash Version: