[protector] Bump Preferences backup version to 3 to mitigate the startup prefs migration.

chrome/browser/protector/protector_service.h

Index: chrome/browser/protector/protector_service.h
diff --git a/chrome/browser/protector/protector_service.h b/chrome/browser/protector/protector_service.h
index ba56448be2ffbb82db462dbb45897532c06587cf..843879b39587b371bda0a6b475000de53cafbc76 100644
--- a/chrome/browser/protector/protector_service.h
+++ b/chrome/browser/protector/protector_service.h
@@ -62,6 +62,10 @@ class ProtectorService : public ProfileKeyedService,
   // backup.
   ProtectedPrefsWatcher* GetPrefsWatcher();
 
+  // Stops observing pref changes and updating the backup. Should be used in
+  // tests only.
+  void StopWatchingPrefsForTesting();
+
   // Returns the most recent change instance or NULL if there are no changes.
   BaseSettingChange* GetLastChange();