Merge "Correct comment on putStringSet"

        /**

         * Set a set of String values in the preferences editor, to be written

         * back once {@link #commit} is called.

         * back once {@link #commit} or {@link #apply} is called.

         * 

         * @param key The name of the preference to modify.

         * @param values The set of new values for the preference.  Passing {@code null}