Add methods to get raw request in WebRequest

Make it possible to get the raw parameters given to the request, with
no escaping. This is needed for features like OAuth, where a signature
is calculated over the parameters to verify their integrity and source.

FauxRequest is extended so the original request doesn't pollute the
fake one. This could be extended so "raw" values could be set and used,
but there isn't a use case for that yet, so it's not done here.

Change-Id: I8710844f21d21cbbf28517b0cc25b0713b506bee
Merge "Add methods to get raw request in WebRequest"