feat(header): implement fmt::Display for several headers

Specifically, `CacheControl`, `Expect`, `Origin`, `Pragma`, `Prefer`,
`PreferenceApplied`, `ReferrerPolicy`, `StrictTransportSecurity`.

src/header/common/authorization.rs

@@ -101,6 +101,12 @@ impl<S: Scheme + Any> Header for Authorization<S> where <S as FromStr>::Err: 'st
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl<S: Scheme> fmt::Display for Authorization<S> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         if let Some(scheme) = <S as Scheme>::scheme() {
             try!(write!(f, "{} ", scheme))
         };
@@ -152,7 +158,6 @@ impl Scheme for Basic {
         if let Some(ref pass) = self.password {
             text.push_str(&pass[..]);
         }
-        
         f.write_str(&encode(text.as_ref()))
     }
 }

src/header/common/cache_control.rs

@@ -65,6 +65,12 @@ impl Header for CacheControl {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for CacheControl {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         fmt_comma_delimited(f, &self[..])
     }
 }

src/header/common/cookie.rs

@@ -55,6 +55,12 @@ impl Header for Cookie {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Cookie {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let cookies = &self.0;
         for (i, cookie) in cookies.iter().enumerate() {
             if i != 0 {
@@ -63,6 +69,7 @@ impl Header for Cookie {
             try!(Display::fmt(&cookie, f));
         }
         Ok(())
+
     }
 }
 

src/header/common/expect.rs

@@ -55,6 +55,12 @@ impl Header for Expect {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Expect {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str("100-continue")
     }
 }

src/header/common/mod.rs

@@ -85,9 +85,8 @@ macro_rules! bench_header(
             fn bench_format(b: &mut Bencher) {
                 let raw = $value.into();
                 let val: $ty = Header::parse_header(&raw).unwrap();
-                let fmt = ::header::HeaderFormatter(&val);
                 b.iter(|| {
-                    format!("{}", fmt);
+                    format!("{}", val);
                 });
             }
         }

src/header/common/origin.rs

@@ -59,7 +59,7 @@ impl Header for Origin {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}://{}", self.scheme, self.host)
+        fmt::Display::fmt(self, f)
     }
 }
 
@@ -83,6 +83,12 @@ impl FromStr for Origin {
     }
 }
 
+impl fmt::Display for Origin {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}://{}", self.scheme, self.host)
+    }
+}
+
 impl PartialEq for Origin {
     fn eq(&self, other: &Origin) -> bool {
         self.scheme == other.scheme && self.host == other.host

src/header/common/pragma.rs

@@ -55,6 +55,12 @@ impl Header for Pragma {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Pragma {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(match *self {
             Pragma::NoCache => "no-cache",
             Pragma::Ext(ref string) => &string[..],

src/header/common/prefer.rs

@@ -66,6 +66,12 @@ impl Header for Prefer {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Prefer {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         fmt_comma_delimited(f, &self[..])
     }
 }

src/header/common/preference_applied.rs

@@ -64,6 +64,13 @@ impl Header for PreferenceApplied {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for PreferenceApplied {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        //TODO: format this without allocating a Vec and cloning contents
         let preferences: Vec<_> = self.0.iter().map(|pref| match pref {
             // The spec ignores parameters in `Preferences-Applied`
             &Preference::Extension(ref name, ref value, _) => Preference::Extension(

src/header/common/referrer_policy.rs

@@ -80,6 +80,12 @@ impl Header for ReferrerPolicy {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for ReferrerPolicy {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         use self::ReferrerPolicy::*;
         f.write_str(match *self {
             NoReferrer => "no-referrer",

src/header/common/strict_transport_security.rs

@@ -130,6 +130,12 @@ impl Header for StrictTransportSecurity {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for StrictTransportSecurity {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         if self.include_subdomains {
             write!(f, "max-age={}; includeSubdomains", self.max_age)
         } else {