Refactoring: Pull Node::disabled() and Node::isInert() down to Element.

Refactoring: Pull Node::disabled() and Node::isInert() down to Element.
https://bugs.webkit.org/show_bug.cgi?id=112085

Reviewed by Hajime Morrita.

Node is too low a level for these methods. The plan is to rename
Element::disabled to isDisabledFormControl and to remove
Element::isEnabledFormControl.

No new tests, just refactoring.

* dom/Element.cpp:
(WebCore::Element::disabled):
(WebCore):
(WebCore::Element::isInert):
* dom/Element.h:
(Element):
* dom/EventDispatcher.cpp:
(WebCore::EventDispatcher::dispatchSimulatedClick):
* dom/GestureEvent.cpp:
(WebCore::GestureEventDispatchMediator::dispatchEvent):
* dom/MouseEvent.cpp:
(WebCore::MouseEventDispatchMediator::dispatchEvent):
* dom/Node.cpp:
(WebCore::Node::handleLocalEvents):
(WebCore::Node::willRespondToMouseMoveEvents):
(WebCore::Node::willRespondToMouseClickEvents):
(WebCore::Node::willRespondToTouchEvents):
* dom/Node.h:
(Node):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@146744 268f45cc-cd09-0410-ab3c-d52691b4dbfc