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

chrome_frame/external_tab.cc

Index: chrome_frame/external_tab.cc
diff --git a/chrome_frame/external_tab.cc b/chrome_frame/external_tab.cc
index ca402d9a0882c54ae65a033b0f48c3e7c3480cdb..0d2609f08135ac80af0d2f7750dafd498607fa99 100644
--- a/chrome_frame/external_tab.cc
+++ b/chrome_frame/external_tab.cc
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 #include "chrome_frame/external_tab.h"
-#include "base/singleton.h"
+#include "base/lazy_instance.h"
 #include "base/tracked.h"
 #include "base/task.h"
 #include "base/waitable_event.h"
@@ -14,7 +14,8 @@ DISABLE_RUNNABLE_METHOD_REFCOUNT(ExternalTabProxy);
 DISABLE_RUNNABLE_METHOD_REFCOUNT(UIDelegate);
 
 namespace {
-  Singleton<ChromeProxyFactory> g_proxy_factory;
+  static base::LazyInstance<ChromeProxyFactory> g_proxy_factory(
+      base::LINKER_INITIALIZED);
 
   struct UserDataHolder : public SyncMessageContext {
     explicit UserDataHolder(void* p) : data(p) {}
@@ -24,7 +25,7 @@ namespace {
 
 
 ExternalTabProxy::ExternalTabProxy() : state_(NONE), tab_(0), tab_wnd_(NULL),
-    chrome_wnd_(NULL), proxy_factory_(g_proxy_factory.get()), proxy_(NULL),
+    chrome_wnd_(NULL), proxy_factory_(g_proxy_factory.Pointer()), proxy_(NULL),
     ui_delegate_(NULL) {
 }