fmt: skip malloc test under race detector

Fixes #10778.

Change-Id: I09aab55dec429ec4a023e5ad591b929563cef0d9
Reviewed-on: https://go-review.googlesource.com/9855Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/fmt/fmt_test.go

@@ -949,11 +949,13 @@ var mallocTest = []struct {
 var _ bytes.Buffer
 
 func TestCountMallocs(t *testing.T) {
-	if testing.Short() {
+	switch {
+	case testing.Short():
 		t.Skip("skipping malloc count in short mode")
-	}
-	if runtime.GOMAXPROCS(0) > 1 {
+	case runtime.GOMAXPROCS(0) > 1:
 		t.Skip("skipping; GOMAXPROCS>1")
+	case raceenabled:
+		t.Skip("skipping malloc count under race detector")
 	}
 	for _, mt := range mallocTest {
 		mallocs := testing.AllocsPerRun(100, mt.fn)

src/fmt/norace_test.go

+// Copyright 2015 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 fmt_test
+
+const raceenabled = false

src/fmt/race_test.go

+// Copyright 2015 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 fmt_test
+
+const raceenabled = true