Threaded HTML parser fails resources/plain-text-unsafe.dat
https://bugs.webkit.org/show_bug.cgi?id=110538

Reviewed by Eric Seidel.

With this patch, the background HTML parser passes all tests in plain-text-unsafe.dat.

No new tests because covered by existing tests.

* html/parser/BackgroundHTMLParser.cpp:
(WebCore::tokenExitsSVG):
(WebCore):
(WebCore::tokenExitsMath):
(WebCore::BackgroundHTMLParser::simulateTreeBuilder):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143830 268f45cc-cd09-0410-ab3c-d52691b4dbfc