Remove unnecessary calls to Node::disabled for <meter>, <progress>, and <output>
https://bugs.webkit.org/show_bug.cgi?id=112767

Reviewed by Kent Tamura.

This is part of a refactoring to move Node::disabled to HTMLFormControlElement::disabled.
The concept of disabled is just a form control element one.

HTMLMeterElement, HTMLOutputElement, and HTMLProgressElement never
have disabled() return true, so we can remove the call. In addition,
HTMLMeterElement and HTMLProgressElement no longer inherit from
HTMLFormControlElement, so we don't need to override supportsFocus.

No new tests because no behavior change.

* html/HTMLMeterElement.cpp:
* html/HTMLMeterElement.h:
* html/HTMLOutputElement.cpp:
(WebCore::HTMLOutputElement::supportsFocus):
* html/HTMLProgressElement.cpp:
* html/HTMLProgressElement.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146417 268f45cc-cd09-0410-ab3c-d52691b4dbfc