Revert of Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/dictionary_hash_store_contents.cc

Index: components/user_prefs/tracked/dictionary_hash_store_contents.cc
diff --git a/components/user_prefs/tracked/dictionary_hash_store_contents.cc b/components/user_prefs/tracked/dictionary_hash_store_contents.cc
index 288c1bf45dba68226b4261c44a6e0a5c5079b164..6bddb6591f86cec3d9e97067f057225829391275 100644
--- a/components/user_prefs/tracked/dictionary_hash_store_contents.cc
+++ b/components/user_prefs/tracked/dictionary_hash_store_contents.cc
@@ -26,16 +26,6 @@
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterDictionaryPref(kPreferenceMACs);
   registry->RegisterStringPref(kSuperMACPref, std::string());
-}
-
-bool DictionaryHashStoreContents::IsCopyable() const {
-  return false;
-}
-
-std::unique_ptr<HashStoreContents> DictionaryHashStoreContents::MakeCopy()
-    const {
-  NOTREACHED() << "DictionaryHashStoreContents does not support MakeCopy";
-  return nullptr;
 }
 
 base::StringPiece DictionaryHashStoreContents::GetUMASuffix() const {
@@ -131,4 +121,4 @@
     storage_->Set(kPreferenceMACs, macs_dict);
   }
   return macs_dict;
-}
+}