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

net/socket/ssl_client_socket_mac.cc

Index: net/socket/ssl_client_socket_mac.cc
diff --git a/net/socket/ssl_client_socket_mac.cc b/net/socket/ssl_client_socket_mac.cc
index fb0c26eceb882867058dc3d7bb7239e307bf82aa..488beebb2474b5994d1c8afe8aee9146ddf2b86c 100644
--- a/net/socket/ssl_client_socket_mac.cc
+++ b/net/socket/ssl_client_socket_mac.cc
@@ -11,8 +11,8 @@
 
 #include <algorithm>
 
+#include "base/lazy_instance.h"
 #include "base/mac/scoped_cftyperef.h"
-#include "base/singleton.h"
 #include "base/string_util.h"
 #include "net/base/address_list.h"
 #include "net/base/cert_verifier.h"
@@ -475,7 +475,7 @@ class EnabledCipherSuites {
   const std::vector<SSLCipherSuite>& ciphers() const { return ciphers_; }
 
  private:
-  friend struct DefaultSingletonTraits<EnabledCipherSuites>;
+  friend struct base::DefaultLazyInstanceTraits<EnabledCipherSuites>;
   EnabledCipherSuites();
   ~EnabledCipherSuites() {}
 
@@ -484,6 +484,9 @@ class EnabledCipherSuites {
   DISALLOW_COPY_AND_ASSIGN(EnabledCipherSuites);
 };
 
+static base::LazyInstance<EnabledCipherSuites> g_enabled_cipher_suites(
+    base::LINKER_INITIALIZED);
+
 EnabledCipherSuites::EnabledCipherSuites() {
   SSLContextRef ssl_context;
   OSStatus status = SSLNewContext(false, &ssl_context);
@@ -786,7 +789,7 @@ int SSLClientSocketMac::InitializeSSLContext() {
     return NetErrorFromOSStatus(status);
 
   std::vector<SSLCipherSuite> enabled_ciphers =
-      Singleton<EnabledCipherSuites>::get()->ciphers();
+      g_enabled_cipher_suites.Get().ciphers();
 
   CipherSuiteIsDisabledFunctor is_disabled_cipher(
       ssl_config_.disabled_cipher_suites);