http: shut up a false Transport warning on Windows

Fixes #2057

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5269044

src/pkg/http/Makefile

@@ -24,4 +24,9 @@ GOFILES=\
 	transfer.go\
 	transport.go\
 
+GOFILES_windows=\
+	transport_windows.go\
+	
+GOFILES+=$(GOFILES_$(GOOS))
+
 include ../../Make.pkg

src/pkg/http/transport.go

@@ -489,12 +489,24 @@ func (pc *persistConn) expectingResponse() bool {
 	return pc.numExpectedResponses > 0
 }
 
+var remoteSideClosedFunc func(os.Error) bool // or nil to use default
+
+func remoteSideClosed(err os.Error) bool {
+	if err == os.EOF || err == os.EINVAL {
+		return true
+	}
+	if remoteSideClosedFunc != nil {
+		return remoteSideClosedFunc(err)
+	}
+	return false
+}
+
 func (pc *persistConn) readLoop() {
 	alive := true
 	for alive {
 		pb, err := pc.br.Peek(1)
 		if err != nil {
-			if (err == os.EOF || err == os.EINVAL) && !pc.expectingResponse() {
+			if remoteSideClosed(err) && !pc.expectingResponse() {
 				// Remote side closed on us.  (We probably hit their
 				// max idle timeout)
 				pc.close()

src/pkg/http/transport_windows.go

@@ -0,0 +1,21 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"os"
+	"net"
+)
+
+func init() {
+	remoteSideClosedFunc = func(err os.Error) (out bool) {
+		op, ok := err.(*net.OpError)
+		if ok && op.Op == "WSARecv" && op.Net == "tcp" && op.Error == os.Errno(10058) {
+			// TODO(bradfitz): find the symbol for 10058
+			return true
+		}
+		return false
+	}
+}