http/cgi: correctly set request Content-Type

R=bradfitz
CC=golang-dev
https://golang.org/cl/4433087

src/pkg/http/cgi/child.go

@@ -84,6 +84,10 @@ func RequestFromMap(params map[string]string) (*http.Request, os.Error) {
 		r.ContentLength = clen
 	}
 
+	if ct := params["CONTENT_TYPE"]; ct != "" {
+		r.Header.Set("Content-Type", ct)
+	}
+
 	// Copy "HTTP_FOO_BAR" variables to "Foo-Bar" Headers
 	for k, v := range params {
 		if !strings.HasPrefix(k, "HTTP_") || skipHeader[k] {

src/pkg/http/cgi/child_test.go

@@ -20,6 +20,7 @@ func TestRequest(t *testing.T) {
 		"HTTP_FOO_BAR":    "baz",
 		"REQUEST_URI":     "/path?a=b",
 		"CONTENT_LENGTH":  "123",
+		"CONTENT_TYPE":    "text/xml",
 		"HTTPS":           "1",
 		"REMOTE_ADDR":     "5.6.7.8",
 	}
@@ -37,6 +38,9 @@ func TestRequest(t *testing.T) {
 		// Tests that we don't put recognized headers in the map
 		t.Errorf("expected User-Agent %q; got %q", e, g)
 	}
+	if g, e := req.Header.Get("Content-Type"), "text/xml"; e != g {
+		t.Errorf("expected Content-Type %q; got %q", e, g)
+	}
 	if g, e := req.ContentLength, int64(123); e != g {
 		t.Errorf("expected ContentLength %d; got %d", e, g)
 	}