Merge "Don't send null data call list response"

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

import java.util.Objects;

        public void requestDataCallList(@NonNull DataServiceCallback callback) {

            // The default implementation is to return unsupported.

            callback.onRequestDataCallListComplete(DataServiceCallback.RESULT_ERROR_UNSUPPORTED,

                    null);

                    Collections.EMPTY_LIST);

        }

        private void registerForDataCallListChanged(IDataServiceCallback callback) {