Tests that XHR redirects preserve request body.
POST http://127.0.0.1:8000/devtools/network/resources/redirect.cgi?status=301&ttl=1
actual http method was: POST
request body: [LOST]
GET http://127.0.0.1:8000/devtools/network/resources/redirect.cgi?status=301&ttl=0
actual http method was: GET
request body: []
POST http://127.0.0.1:8000/devtools/network/resources/redirect.cgi?status=307&ttl=1
actual http method was: POST
request body: [PRESERVED]
POST http://127.0.0.1:8000/devtools/network/resources/redirect.cgi?status=307&ttl=0
actual http method was: POST
request body: [PRESERVED]