Merge "Add threading comments for the delegate initiation callback"

     * @param delegatorViewId identifier of the delegator editor view for which handwriting mode

     *     should be initiated

     * @param initiationCallback callback called when a stylus {@link MotionEvent} occurs within

     *     this view's bounds

     *     this view's bounds. This will be called from the UI thread.

     */

    public HandwritingDelegateConfiguration(

            @IdRes int delegatorViewId, @NonNull Runnable initiationCallback) {

    /**

     * Returns the callback which should be called when a stylus {@link MotionEvent} occurs within

     * the delegate view's bounds.

     * the delegate view's bounds. The callback should only be called from the UI thread.

     */

    @NonNull

    public Runnable getInitiationCallback() {