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

chrome/browser/sync/util/cryptographer_unittest.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/util/cryptographer.h"
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string_util.h"
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               OnEncryptedTypesChanged(syncable::GetAllRealModelTypes(),
                                       false));
 
   // Set all encrypted types
   encrypted_types = syncable::GetAllRealModelTypes();
   cryptographer.SetEncryptedTypesForTest(encrypted_types);
   cryptographer.UpdateNigoriFromEncryptedTypes(&nigori);
   cryptographer2.UpdateEncryptedTypesFromNigori(nigori);
   EXPECT_EQ(encrypted_types, cryptographer.GetEncryptedTypes());
   EXPECT_EQ(encrypted_types, cryptographer2.GetEncryptedTypes());
+
+  // Receiving an empty nigori should not reset any encrypted types.
+  Mock::VerifyAndClearExpectations(&observer);
+  EXPECT_CALL(observer,
+              OnEncryptedTypesChanged(syncable::GetAllRealModelTypes(),
+                                      false));
+  nigori = sync_pb::NigoriSpecifics();
+  cryptographer.UpdateEncryptedTypesFromNigori(nigori);
+  EXPECT_EQ(encrypted_types, cryptographer.GetEncryptedTypes());
 }
 
 TEST(CryptographerTest, EncryptEverythingExplicit) {
   ModelTypeSet real_types = syncable::GetAllRealModelTypes();
   sync_pb::NigoriSpecifics specifics;
   specifics.set_encrypt_everything(true);
 
   Cryptographer cryptographer;
   StrictMock<MockObserver> observer;
   cryptographer.AddObserver(&observer);
@@ skipping 112 matching lines @@
         *iter == syncable::BOOKMARKS)
       EXPECT_EQ(1U, encrypted_types.count(*iter));
     else
       EXPECT_EQ(0U, encrypted_types.count(*iter));
   }
 
   cryptographer.RemoveObserver(&observer);
 }
 
 }  // namespace browser_sync