Comb up ownership things.

chrome/browser/chromeos/login/user_manager.h

Index: chrome/browser/chromeos/login/user_manager.h
diff --git a/chrome/browser/chromeos/login/user_manager.h b/chrome/browser/chromeos/login/user_manager.h
index 19f0f7f9d3c7894c528fcdaf9bd316b2d386caa5..6a542eb09c3c05c0d4720842e8b21254e45ad51a 100644
--- a/chrome/browser/chromeos/login/user_manager.h
+++ b/chrome/browser/chromeos/login/user_manager.h
@@ -12,6 +12,7 @@
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/ref_counted.h"
+#include "base/synchronization/lock.h"
 #include "chrome/browser/chromeos/login/user_image_loader.h"
 #include "content/common/notification_observer.h"
 #include "content/common/notification_registrar.h"
@@ -20,6 +21,10 @@
 class FilePath;
 class PrefService;
 
+namespace base {
+template<typename> struct DefaultLazyInstanceTraits;
+}
+
 namespace chromeos {
 class RemoveUserDelegate;
 
@@ -149,7 +154,9 @@ class UserManager : public UserImageLoader::Delegate,
   User logged_in_user_;
 
   // Cached flag of whether currently logged-in user is owner or not.
+  // May be accessed on different threads, requires locking.
   bool current_user_is_owner_;
+  mutable base::Lock current_user_is_owner_lock_;
 
   // Cached flag of whether the currently logged-in user existed before this
   // login.
@@ -160,6 +167,8 @@ class UserManager : public UserImageLoader::Delegate,
 
   NotificationRegistrar registrar_;
 
+  friend struct base::DefaultLazyInstanceTraits<UserManager>;
+
   DISALLOW_COPY_AND_ASSIGN(UserManager);
 };