http2: remove unused errors

errInvalidHeaderFieldName and errInvalidHeaderFieldValue are unused
since CL 19726.

errInvalidTrailers and errPseudoTrailers were added in CL 18367 but
never used.

Change-Id: I8d4c971f3eaee8b9405e7511645a641c0e513898
Reviewed-on: https://go-review.googlesource.com/c/net/+/220458
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

http2/http2.go

@@ -19,7 +19,6 @@ package http2 // import "golang.org/x/net/http2"
 import (
 	"bufio"
 	"crypto/tls"
-	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -173,11 +172,6 @@ func (s SettingID) String() string {
 	return fmt.Sprintf("UNKNOWN_SETTING_%d", uint16(s))
 }
 
-var (
-	errInvalidHeaderFieldName  = errors.New("http2: invalid header field name")
-	errInvalidHeaderFieldValue = errors.New("http2: invalid header field value")
-)
-
 // validWireHeaderFieldName reports whether v is a valid header field
 // name (key). See httpguts.ValidHeaderName for the base rules.
 //

http2/transport.go

@@ -2198,8 +2198,6 @@ func (rl *clientConnReadLoop) processData(f *DataFrame) error {
 	return nil
 }
 
-var errInvalidTrailers = errors.New("http2: invalid trailers")
-
 func (rl *clientConnReadLoop) endStream(cs *clientStream) {
 	// TODO: check that any declared content-length matches, like
 	// server.go's (*stream).endStream method.
@@ -2430,7 +2428,6 @@ func (cc *ClientConn) writeStreamReset(streamID uint32, code ErrCode, err error)
 var (
 	errResponseHeaderListSize = errors.New("http2: response header list larger than advertised limit")
 	errRequestHeaderListSize  = errors.New("http2: request header list larger than peer's advertised limit")
-	errPseudoTrailers         = errors.New("http2: invalid pseudo header in trailers")
 )
 
 func (cc *ClientConn) logf(format string, args ...interface{}) {