Reviewed by Alexey Proskuryakov.

        fast/encoding/japanese-encoding-mix.html fails on Tiger after enabling HTML5 Lexer
        https://bugs.webkit.org/show_bug.cgi?id=40725

        Qt and Tiger seem to have encoding problems that swallow the --
        characters that terminate the comment.  We can avoid those problems by
        inserting a space before the -->.  We're losing coverage of these
        issues, but I'm not sure we should be in the business of debugging
        these encoders unless there's a security problem.

        Thanks to ap for investigating and finding this workaround.

        * fast/encoding/japanese-encoding-mix.html:
        * platform/mac-tiger/Skipped:
        * platform/qt/Skipped:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@65211 268f45cc-cd09-0410-ab3c-d52691b4dbfc