net/http: disable an alloc test under the race detector

LGTM=dvyukov
R=dvyukov
CC=golang-codereviews
https://golang.org/cl/70200052

src/pkg/net/http/header.go

@@ -13,6 +13,8 @@ import (
 	"time"
 )
 
+var raceEnabled = false // set by race.go
+
 // A Header represents the key-value pairs in an HTTP header.
 type Header map[string][]string
 

src/pkg/net/http/header_test.go

@@ -192,9 +192,12 @@ func BenchmarkHeaderWriteSubset(b *testing.B) {
 	}
 }
 
-func TestHeaderWriteSubsetMallocs(t *testing.T) {
+func TestHeaderWriteSubsetAllocs(t *testing.T) {
 	if testing.Short() {
-		t.Skip("skipping malloc count in short mode")
+		t.Skip("skipping alloc test in short mode")
+	}
+	if raceEnabled {
+		t.Skip("skipping test under race detector")
 	}
 	if runtime.GOMAXPROCS(0) > 1 {
 		t.Skip("skipping; GOMAXPROCS>1")
@@ -204,6 +207,6 @@ func TestHeaderWriteSubsetMallocs(t *testing.T) {
 		testHeader.WriteSubset(&buf, nil)
 	})
 	if n > 0 {
-		t.Errorf("mallocs = %g; want 0", n)
+		t.Errorf("allocs = %g; want 0", n)
 	}
 }

src/pkg/net/http/race.go

@@ -0,0 +1,11 @@
+// Copyright 2014 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.
+
+// +build race
+
+package http
+
+func init() {
+	raceEnabled = true
+}