net/http: update bundled http2

Updates x/net/http2 to git rev 5916dcb1 for:

* http2, lex/httplex: make Transport reject bogus headers before sending
  https://golang.org/cl/23229

* http2: reject more trailer values
  https://golang.org/cl/23230

Fixes #14048
Fixes #14188

Change-Id: Iaa8beca6e005267a3e849a10013eb424a882f2bb
Reviewed-on: https://go-review.googlesource.com/23234
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/net/http/http.go b/src/net/http/http.go
index a121628632..4d088a5bb1 100644
--- a/src/net/http/http.go
+++ b/src/net/http/http.go
@@ -6,6 +6,8 @@ package http
 
 import (
 	"strings"
+
+	"golang.org/x/net/lex/httplex"
 )
 
 // maxInt64 is the effective "infinite" value for the Server and
@@ -35,3 +37,7 @@ func removeEmptyPort(host string) string {
 	}
 	return host
 }
+
+func isNotToken(r rune) bool {
+	return !httplex.IsTokenRune(r)
+}