Introduce a new framework for back-and-forth tracked/protected preferences migration.

chrome/browser/prefs/profile_pref_store_manager.h

Index: chrome/browser/prefs/profile_pref_store_manager.h
diff --git a/chrome/browser/prefs/profile_pref_store_manager.h b/chrome/browser/prefs/profile_pref_store_manager.h
index cf515511ce1859451fda1ecf6527ed0b01653971..fa2456bebcfc9823b7087c84c17bdf801141cae4 100644
--- a/chrome/browser/prefs/profile_pref_store_manager.h
+++ b/chrome/browser/prefs/profile_pref_store_manager.h
@@ -108,10 +108,6 @@ class ProfilePrefStoreManager {
   // if |kPlatformSupportsPreferenceTracking|.
   scoped_ptr<PrefHashStoreImpl> GetPrefHashStoreImpl();
 
-  // Returns a PrefHashStore that is a copy of the current state of the real
-  // hash store.
-  scoped_ptr<PrefHashStore> CopyPrefHashStore();
-
   const base::FilePath profile_path_;
   const std::vector<PrefHashFilter::TrackedPreferenceMetadata>
       tracking_configuration_;