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

chrome/browser/chromeos/login/screen_locker.cc

Index: chrome/browser/chromeos/login/screen_locker.cc
diff --git a/chrome/browser/chromeos/login/screen_locker.cc b/chrome/browser/chromeos/login/screen_locker.cc
index f59307b41ea1bfa47f6e33f951aedee93a636f23..2167650ae4e2a76302669eccb402be4ea49fae4c 100644
--- a/chrome/browser/chromeos/login/screen_locker.cc
+++ b/chrome/browser/chromeos/login/screen_locker.cc
@@ -16,9 +16,9 @@
 #include "app/resource_bundle.h"
 #include "app/x11_util.h"
 #include "base/command_line.h"
+#include "base/lazy_instance.h"
 #include "base/metrics/histogram.h"
 #include "base/message_loop.h"
-#include "base/singleton.h"
 #include "base/string_util.h"
 #include "base/timer.h"
 #include "base/utf_string_conversions.h"
@@ -194,6 +194,9 @@ class ScreenLockObserver : public chromeos::ScreenLockLibrary::Observer,
   DISALLOW_COPY_AND_ASSIGN(ScreenLockObserver);
 };
 
+static base::LazyInstance<ScreenLockObserver> g_screen_lock_observer(
+    base::LINKER_INITIALIZED);
+
 // A ScreenLock window that covers entire screen to keep the keyboard
 // focus/events inside the grab widget.
 class LockWindow : public views::WidgetGtk {
@@ -901,7 +904,7 @@ void ScreenLocker::UnlockScreenFailed() {
 
 // static
 void ScreenLocker::InitClass() {
-  Singleton<ScreenLockObserver>::get();
+  g_screen_lock_observer.Get();
 }
 
 ////////////////////////////////////////////////////////////////////////////////