Make members of Singleton<T> private and only visible to the singleton type.

base/i18n/number_formatting.cc

Index: base/i18n/number_formatting.cc
diff --git a/base/i18n/number_formatting.cc b/base/i18n/number_formatting.cc
index 7a69294a76fc547b8f7ef0b7b93e1234fc27a589..df6af1462c2aeb09bf9f92ca7bd0ed0a95b76681 100644
--- a/base/i18n/number_formatting.cc
+++ b/base/i18n/number_formatting.cc
@@ -6,7 +6,8 @@
 
 #include "base/format_macros.h"
 #include "base/logging.h"
-#include "base/singleton.h"
+#include "base/lazy_instance.h"
+#include "base/scoped_ptr.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "unicode/numfmt.h"
@@ -16,25 +17,26 @@ namespace base {
 
 namespace {
 
-struct NumberFormatSingletonTraits
-    : public DefaultSingletonTraits<icu::NumberFormat> {
-  static icu::NumberFormat* New() {
+struct NumberFormatWrapper {
+  NumberFormatWrapper() {
+    // There's no ICU call to destroy a NumberFormat object other than
+    // operator delete, so use the default Delete, which calls operator delete.
+    // This can cause problems if a different allocator is used by this file
+    // than by ICU.
     UErrorCode status = U_ZERO_ERROR;
-    icu::NumberFormat* formatter = icu::NumberFormat::createInstance(status);
+    number_format.reset(icu::NumberFormat::createInstance(status));
     DCHECK(U_SUCCESS(status));
-    return formatter;
   }
-  // There's no ICU call to destroy a NumberFormat object other than
-  // operator delete, so use the default Delete, which calls operator delete.
-  // This can cause problems if a different allocator is used by this file than
-  // by ICU.
+
+  scoped_ptr<icu::NumberFormat> number_format;
 };
 
 }  // namespace
 
+static LazyInstance<NumberFormatWrapper> g_number_format(LINKER_INITIALIZED);
+
 string16 FormatNumber(int64 number) {
-  icu::NumberFormat* number_format =
-      Singleton<icu::NumberFormat, NumberFormatSingletonTraits>::get();
+  icu::NumberFormat* number_format = g_number_format.Get().number_format.get();
 
   if (!number_format) {
     // As a fallback, just return the raw number in a string.