Move WebVTTToken off of MarkupTokenBase
https://bugs.webkit.org/show_bug.cgi?id=109410

Reviewed by Tony Gentilcore.

This introduces a small amount of "copy/paste" code
but actually makes WebVTTToken much smaller and simpler!
This also frees the HTMLParser to have its Token class
back to itself so we can tune it to make HTML faster.

* html/track/WebVTTToken.h:
(WebVTTToken):
(WebCore::WebVTTToken::WebVTTToken):
(WebCore::WebVTTToken::appendToName):
(WebCore::WebVTTToken::type):
(WebCore::WebVTTToken::name):
(WebCore::WebVTTToken::ensureIsCharacterToken):
(WebCore::WebVTTToken::appendToCharacter):
(WebCore::WebVTTToken::beginEmptyStartTag):
(WebCore::WebVTTToken::beginStartTag):
(WebCore::WebVTTToken::beginEndTag):
(WebCore::WebVTTToken::beginTimestampTag):
(WebCore::WebVTTToken::makeEndOfFile):
(WebCore::WebVTTToken::clear):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142484 268f45cc-cd09-0410-ab3c-d52691b4dbfc