time: fix registry zone info lookup on Windows

registry.ReadSubKeyNames requires QUERY access right in addition to
ENUMERATE_SUB_KEYS.

This was making TestLocalZoneAbbr fail on Windows 7 in Paris/Madrid
timezone. It succeeded on Windows 8 because timezone name changed from
"Paris/Madrid" to "Romance Standard Time", the latter being matched by
an abbrs entry.

Change-Id: I791287ba9d1b3556246fa4e9e1604a1fbba1f5e6
Reviewed-on: https://go-review.googlesource.com/9809Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/export_windows_test.go

@@ -8,3 +8,7 @@ func ForceAusForTesting() {
 	ResetLocalOnceForTest()
 	localOnce.Do(initAusTestingZone)
 }
+
+func ToEnglishName(stdname, dstname string) (string, error) {
+	return toEnglishName(stdname, dstname)
+}

src/time/zoneinfo_windows.go

@@ -49,7 +49,7 @@ func matchZoneKey(zones registry.Key, kname string, stdname, dstname string) (ma
 // toEnglishName searches the registry for an English name of a time zone
 // whose zone names are stdname and dstname and returns the English name.
 func toEnglishName(stdname, dstname string) (string, error) {
-	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones`, registry.ENUMERATE_SUB_KEYS)
+	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones`, registry.ENUMERATE_SUB_KEYS|registry.QUERY_VALUE)
 	if err != nil {
 		return "", err
 	}

src/time/zoneinfo_windows_test.go

@@ -5,6 +5,7 @@
 package time_test
 
 import (
+	"internal/syscall/windows/registry"
 	"testing"
 	. "time"
 )
@@ -33,3 +34,27 @@ func TestAusZoneAbbr(t *testing.T) {
 	defer ForceUSPacificForTesting()
 	testZoneAbbr(t)
 }
+
+func TestToEnglishName(t *testing.T) {
+	const want = "Central Europe Standard Time"
+	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\`+want, registry.READ)
+	if err != nil {
+		t.Fatalf("cannot open CEST time zone information from registry: %s", err)
+	}
+	defer k.Close()
+	std, _, err := k.GetStringValue("Std")
+	if err != nil {
+		t.Fatalf("cannot read CEST Std registry key: %s", err)
+	}
+	dlt, _, err := k.GetStringValue("Dlt")
+	if err != nil {
+		t.Fatalf("cannot read CEST Dlt registry key: %s", err)
+	}
+	name, err := ToEnglishName(std, dlt)
+	if err != nil {
+		t.Fatalf("toEnglishName failed: %s", err)
+	}
+	if name != want {
+		t.Fatalf("english name: %q, want: %q", name, want)
+	}
+}