Get rid of the ability to unregister preferences.

chrome/browser/chromeos/login/oauth2_login_manager.h

Index: chrome/browser/chromeos/login/oauth2_login_manager.h
diff --git a/chrome/browser/chromeos/login/oauth2_login_manager.h b/chrome/browser/chromeos/login/oauth2_login_manager.h
index 1e55f04d20ecf23ac55844449cb3c70f0bf3fedf..3f358d56e9d0b982ac05b0272035e3ec1be3cba3 100644
--- a/chrome/browser/chromeos/login/oauth2_login_manager.h
+++ b/chrome/browser/chromeos/login/oauth2_login_manager.h
@@ -17,6 +17,7 @@
 #include "net/url_request/url_request_context_getter.h"
 
 class GoogleServiceAuthError;
+class PrefRegistrySyncable;
 class Profile;
 class TokenService;
 
@@ -31,6 +32,8 @@ class OAuth2LoginManager : public OAuthLoginManager,
   explicit OAuth2LoginManager(OAuthLoginManager::Delegate* delegate);
   virtual ~OAuth2LoginManager();
 
+  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+
   // OAuthLoginManager overrides.
   virtual void RestorePolicyTokens(
       net::URLRequestContextGetter* auth_request_context) OVERRIDE;
@@ -73,7 +76,7 @@ class OAuth2LoginManager : public OAuthLoginManager,
   // observer events.
   TokenService* SetupTokenService();
 
-  // Removes legacy tokens form OAuth1 flow.
+  // Removes legacy tokens from OAuth1 flow.
   void RemoveLegacyTokens();
 
   // Records OAuth2 tokens fetched through either policy fetcher or cookies-to-