feat(http): add optional serialization of common types via serde

This is behind a Cargo feature to avoid forcing downstream users to
depend on `serde`. It is needed for Servo IPC to work.

src/http/mod.rs

@@ -7,6 +7,9 @@ use header::Headers;
 use version::HttpVersion;
 use version::HttpVersion::{Http10, Http11};
 
+#[cfg(feature = "serde-serialization")]
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
 pub use self::message::{HttpMessage, RequestHead, ResponseHead, Protocol};
 
 pub mod h1;
@@ -17,6 +20,21 @@ pub mod message;
 #[derive(Clone, PartialEq, Debug)]
 pub struct RawStatus(pub u16, pub Cow<'static, str>);
 
+#[cfg(feature = "serde-serialization")]
+impl Serialize for RawStatus {
+    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer {
+        (self.0, self.1.clone().into_owned()).serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serde-serialization")]
+impl Deserialize for RawStatus {
+    fn deserialize<D>(deserializer: &mut D) -> Result<RawStatus, D::Error> where D: Deserializer {
+        let representation: (u16, String) = try!(Deserialize::deserialize(deserializer));
+        Ok(RawStatus(representation.0, Cow::Owned(representation.1)))
+    }
+}
+
 /// Checks if a connection should be kept alive.
 #[inline]
 pub fn should_keep_alive(version: HttpVersion, headers: &Headers) -> bool {