Reviewed by Adam Roben.

        Add an --html5-parser option to DumpRenderTree to allow testing the new HTML5Lexer
        https://bugs.webkit.org/show_bug.cgi?id=39311

        This flag allows us to run the new HTML5Lexer code.
        Right now all documents parse as empty documents, but
        now that we're able to run the code we can fix that.

        Once we're able to lex a few basic documents I'll add
        an --html5-parser flag to run-webkit-tests so that we test
        running all of the layout tests with the HTML5 parser.

        * DumpRenderTree/mac/DumpRenderTree.mm:
        (resetDefaultsToConsistentValues):
        (initializeGlobalsFromCommandLineOptions):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@59687 268f45cc-cd09-0410-ab3c-d52691b4dbfc