Fixes for HTTP 400 errors from nginx in response to Servo requests.

- Implement conformant albeit non-normative (but as implemented in Firefox, Safari, and Chrome) https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2 by removing whitespace from `Accept` and `Accept-Language` HTTP headers.
- Provide a `Host` header.

components/net/http_loader.rs

@@ -177,7 +177,7 @@ pub fn set_default_accept_language(headers: &mut HeaderMap) {
     // TODO(eijebong): Change this once typed headers are done
     headers.insert(
         header::ACCEPT_LANGUAGE,
-        HeaderValue::from_static("en-US, en; q=0.5"),
+        HeaderValue::from_static("en-US,en;q=0.5"),
     );
 }
 
@@ -1225,7 +1225,17 @@ async fn http_network_or_cache_fetch(
 
     // Step 5.16
     let current_url = http_request.current_url();
-    http_request.headers.remove(header::HOST);
+    if !http_request.headers.contains_key(header::HOST) {
+        let host = if current_url.port().is_none() {
+            current_url.host_str().unwrap().to_string()
+        } else {
+            format!("{}:{}", current_url.host_str().unwrap(), current_url.port().unwrap())
+        };
+        http_request.headers.typed_insert(headers::Host::from(host
+                .parse::<http::uri::Authority>()
+                .unwrap(),
+        ));
+    }
 
     // unlike http_loader, we should not set the accept header
     // here, according to the fetch spec

components/shared/net/quality.rs

@@ -59,9 +59,9 @@ where
         fmt::Display::fmt(&self.item, fmt)?;
         match self.quality.0 {
             1000 => Ok(()),
-            0 => fmt.write_str("; q=0"),
+            0 => fmt.write_str(";q=0"),
             mut x => {
-                fmt.write_str("; q=0.")?;
+                fmt.write_str(";q=0.")?;
                 let mut digits = *b"000";
                 digits[2] = (x % 10) as u8 + b'0';
                 x /= 10;
@@ -81,7 +81,7 @@ pub fn quality_to_value(q: Vec<QualityItem<Mime>>) -> HeaderValue {
         &q.iter()
             .map(|q| q.to_string())
             .collect::<Vec<String>>()
-            .join(", "),
+            .join(","),
     )
     .unwrap()
 }