[TSAN] Fix TSAN error in i18n RTL.

base/i18n/rtl.cc

Index: base/i18n/rtl.cc
diff --git a/base/i18n/rtl.cc b/base/i18n/rtl.cc
index 2b6bf37706fd4ad52b28024427fa0451fc121c9d..07fd9642d37d203689c86e2083cf6052f1cf515e 100644
--- a/base/i18n/rtl.cc
+++ b/base/i18n/rtl.cc
@@ -9,6 +9,7 @@
 
 #include <algorithm>
 
+#include "base/atomicops.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/i18n/base_i18n_switches.h"
@@ -113,7 +114,8 @@ namespace base {
 namespace i18n {
 
 // Represents the locale-specific ICU text direction.
-static TextDirection g_icu_text_direction = UNKNOWN_DIRECTION;
+static subtle::Atomic32 g_icu_text_direction =
+    static_cast<subtle::Atomic32>(UNKNOWN_DIRECTION);
 
 // Convert the ICU default locale to a string.
 std::string GetConfiguredLocale() {
@@ -162,7 +164,10 @@ void SetICUDefaultLocale(const std::string& locale_string) {
   // presence of actual locale data). However,
   // it does not hurt to have it as a sanity check.
   DCHECK(U_SUCCESS(error_code));
-  g_icu_text_direction = UNKNOWN_DIRECTION;
+  subtle::Release_Store(
+      &g_icu_text_direction,
+      static_cast<subtle::Atomic32>(
+          GetTextDirectionForLocaleInStartUp(locale.getName())));
 }
 
 bool IsRTL() {
@@ -170,11 +175,11 @@ bool IsRTL() {
 }
 
 bool ICUIsRTL() {
-  if (g_icu_text_direction == UNKNOWN_DIRECTION) {
-    const icu::Locale& locale = icu::Locale::getDefault();
-    g_icu_text_direction = GetTextDirectionForLocaleInStartUp(locale.getName());
-  }
-  return g_icu_text_direction == RIGHT_TO_LEFT;
+  // Note: There is still  a race if this is executed between the
+  // icu::Locale::setDefault and the g_icu_text_direction store
+  // that happens in SetICUDefaultLocale.
+  return static_cast<TextDirection>(
+             subtle::Acquire_Load(&g_icu_text_direction)) == RIGHT_TO_LEFT;
 }
 
 TextDirection GetTextDirectionForLocaleInStartUp(const char* locale_name) {