content_sniffed
Description:
This signal is emitted after [signal@Message:SoupMessage:got-headerss].
If content sniffing is disabled, or no content sniffing will be performed, due to the sniffer deciding to trust the Content-Type sent by the 
      server, this signal is emitted immediately after [signal@Message:SoupMessage:got-headerss], and type is 
      null.
Parameters:
| type | the content type that we got from sniffing | 
| params | a GenericSet with the parameters |