Merge "Make unicodeWrap() return null if the input string is null." into mnc-dev

     *        See {@link TextDirectionHeuristics} for pre-defined heuristics.

     * @param isolate Whether to directionally isolate the string to prevent it from garbling the

     *     content around it

     * @return Input string after applying the above processing.

     * @return Input string after applying the above processing. {@code null} if {@code str} is

     *     {@code null}.

     */

    public String unicodeWrap(String str, TextDirectionHeuristic heuristic, boolean isolate) {

        if (str == null) return null;

        final boolean isRtl = heuristic.isRtl(str, 0, str.length());

        StringBuilder result = new StringBuilder();

        if (getStereoReset() && isolate) {