Get rid of the ability to unregister preferences.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index fe23605e8fd7924c534ce310d87cec693e0e98f0..3451ffc94d96aefc24a428bdd86e0c5cb5e49d02 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -787,12 +787,6 @@ const char kChromeOSReleaseNotesVersion[] = "settings.release_notes.version";
 // A boolean pref that uses shared proxies.
 const char kUseSharedProxies[] = "settings.use_shared_proxies";
 
-// A string prefs for OAuth1 token.
-const char kOAuth1Token[] = "settings.account.oauth1_token";
-
-// A string prefs for OAuth1 secret.
-const char kOAuth1Secret[] = "settings.account.oauth1_secret";
-
 // A boolean pref that enables the (private) pepper GetID() call.
 const char kEnableCrosDRM[] = "settings.privacy.drm_enabled";