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

printing/backend/print_backend_cups.cc

Index: printing/backend/print_backend_cups.cc
diff --git a/printing/backend/print_backend_cups.cc b/printing/backend/print_backend_cups.cc
index 9fbf2ab2afca733292a11c282414c000736863a4..e75a8003edbb7adc3a3d9b0e60a8ceb440e79fd9 100644
--- a/printing/backend/print_backend_cups.cc
+++ b/printing/backend/print_backend_cups.cc
@@ -12,9 +12,9 @@
 #include <pthread.h>
 
 #include "base/file_util.h"
+#include "base/lazy_instance.h"
 #include "base/lock.h"
 #include "base/logging.h"
-#include "base/singleton.h"
 #include "base/string_number_conversions.h"
 #include "base/values.h"
 #include "googleurl/src/gurl.h"
@@ -66,6 +66,9 @@ class GcryptInitializer {
   }
 };
 
+static base::LazyInstance<GcryptInitializer> g_gcrypt_initializer(
+    base::LINKER_INITIALIZED);
+
 }  // namespace
 #endif
 
@@ -188,7 +191,7 @@ scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
     const DictionaryValue* print_backend_settings) {
 #if !defined(OS_MACOSX)
   // Initialize gcrypt library.
-  Singleton<GcryptInitializer>::get();
+  g_gcrypt_initializer.Get();
 #endif
 
   std::string print_server_url_str;