vendor: upgrade grpc-gateway to v1.2.0

cmd/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/context.go

@@ -15,12 +15,17 @@ import (
 	"google.golang.org/grpc/metadata"
 )
 
-// MetadataHeaderPrefix is prepended to HTTP headers in order to convert them to 
-// gRPC metadata for incoming requests processed by grpc-gateway
+// MetadataHeaderPrefix is the http prefix that represents custom metadata
+// parameters to or from a gRPC call.
 const MetadataHeaderPrefix = "Grpc-Metadata-"
+
+// MetadataPrefix is the prefix for grpc-gateway supplied custom metadata fields.
+const MetadataPrefix = "grpcgateway-"
+
 // MetadataTrailerPrefix is prepended to gRPC metadata as it is converted to
 // HTTP headers in a response handled by grpc-gateway
 const MetadataTrailerPrefix = "Grpc-Trailer-"
+
 const metadataGrpcTimeout = "Grpc-Timeout"
 
 const xForwardedFor = "X-Forwarded-For"
@@ -52,8 +57,12 @@ func AnnotateContext(ctx context.Context, req *http.Request) (context.Context, e
 
 	for key, vals := range req.Header {
 		for _, val := range vals {
-			if key == "Authorization" {
+			// For backwards-compatibility, pass through 'authorization' header with no prefix.
+			if strings.ToLower(key) == "authorization" {
 				pairs = append(pairs, "authorization", val)
+			}
+			if isPermanentHTTPHeader(key) {
+				pairs = append(pairs, strings.ToLower(fmt.Sprintf("%s%s", MetadataPrefix, key)), val)
 				continue
 			}
 			if strings.HasPrefix(key, MetadataHeaderPrefix) {
@@ -141,3 +150,38 @@ func timeoutUnitToDuration(u uint8) (d time.Duration, ok bool) {
 	}
 	return
 }
+
+// isPermanentHTTPHeader checks whether hdr belongs to the list of
+// permenant request headers maintained by IANA.
+// http://www.iana.org/assignments/message-headers/message-headers.xml
+func isPermanentHTTPHeader(hdr string) bool {
+	switch hdr {
+	case
+		"Accept",
+		"Accept-Charset",
+		"Accept-Language",
+		"Accept-Ranges",
+		"Authorization",
+		"Cache-Control",
+		"Content-Type",
+		"Cookie",
+		"Date",
+		"Expect",
+		"From",
+		"Host",
+		"If-Match",
+		"If-Modified-Since",
+		"If-None-Match",
+		"If-Schedule-Tag-Match",
+		"If-Unmodified-Since",
+		"Max-Forwards",
+		"Origin",
+		"Pragma",
+		"Referer",
+		"User-Agent",
+		"Via",
+		"Warning":
+		return true
+	}
+	return false
+}