Use HTMLElementFactory to create equivalent elements in WebVTTElement.

This change forces the calls through the factory so that we create
appropriate sub-classes based upon the passed tag name, rather than
just creating a concrete HTMLElement class with an inappropriate tag


Review URL:

Patch from Tom Sepez <>.

git-svn-id: svn:// bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed