I'd really like to see this inherit from ```<base-http-request>``` rather than the new ```<raw-http-request>```, which seems redundant to me.  Also, I don't think it should be merged with ```<request>```, but probably some of the slots in ```<request>``` could be moved into ```<base-http-request>```.

Could you spell out "parameters" in the slot name instead of abbreviating it?  I think the client and server should use the same terminology, so can you update the server code to use "parameters" where it currently uses "query-values"?  (In a separate pull request.)