[Sync] The cryptographer should be able to handle empty or old nigori nodes.

chrome/browser/sync/util/cryptographer.h

Index: chrome/browser/sync/util/cryptographer.h
diff --git a/chrome/browser/sync/util/cryptographer.h b/chrome/browser/sync/util/cryptographer.h
index e78e3f388a31bd7bed28d2b6ded37ab7d4151b01..992c443900b17b1236bf4813cadac76cd9511fa3 100644
--- a/chrome/browser/sync/util/cryptographer.h
+++ b/chrome/browser/sync/util/cryptographer.h
@@ -182,17 +182,17 @@ class Cryptographer {
   // Return the set of encrypted types.
   syncable::ModelTypeSet GetEncryptedTypes() const;
 
-  // Forwards to SetEncryptedTypes.
-  void SetEncryptedTypesForTest(
+  // Forwards to MergeEncryptedTypes.
+  void MergeEncryptedTypesForTest(
       const syncable::ModelTypeSet& encrypted_types);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(CryptographerTest, PackUnpack);
   typedef std::map<std::string, linked_ptr<const Nigori> > NigoriMap;
 
-  // Changes the set of encrypted types and emits a notification if
-  // necessary.
-  void SetEncryptedTypes(const syncable::ModelTypeSet& encrypted_types);
+  // Merges the given set of encrypted types with the existing set and emits a
+  // notification if necessary.
+  void MergeEncryptedTypes(const syncable::ModelTypeSet& encrypted_types);
 
   void EmitEncryptedTypesChangedNotification();