Replace more ObserverList with base::ObserverList.

sync/test/fake_sync_encryption_handler.h

 // Copyright (c) 2012 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.
 
 #ifndef SYNC_SYNCABLE_TEST_FAKE_SYNC_ENCRYPTION_HANDLER_H_
 #define SYNC_SYNCABLE_TEST_FAKE_SYNC_ENCRYPTION_HANDLER_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 37 matching lines @@
   bool NeedKeystoreKey(syncable::BaseTransaction* const trans) const override;
   bool SetKeystoreKeys(
       const google::protobuf::RepeatedPtrField<google::protobuf::string>& keys,
       syncable::BaseTransaction* const trans) override;
   ModelTypeSet GetEncryptedTypes(
       syncable::BaseTransaction* const trans) const override;
 
   Cryptographer* cryptographer() { return &cryptographer_; }
 
  private:
-  ObserverList<SyncEncryptionHandler::Observer> observers_;
+  base::ObserverList<SyncEncryptionHandler::Observer> observers_;
   ModelTypeSet encrypted_types_;
   bool encrypt_everything_;
   PassphraseType passphrase_type_;
 
   FakeEncryptor encryptor_;
   Cryptographer cryptographer_;
   std::string keystore_key_;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_TEST_FAKE_SYNC_ENCRYPTION_HANDLER_H_