Refactoring: Simplify FormController interface

Refactoring: Simplify FormController interface
https://bugs.webkit.org/show_bug.cgi?id=89951

Reviewed by Kentaro Hara.

- Remove FormController::hasStateForNewFormElements()
  takeStateForFormElement() can check the emptiness, and return an empty
  FormControlState.

- Change the argument of takeStateForFormElement()
  Passing just one HTMLFormControlElementWithState object instead of two
  AtomicStringImpl. This is a preparation to use
  HTMLFormControlElementWithState::form() in FormController.

No new tests. Just a refactoring.

* html/FormController.cpp:
(WebCore::FormController::takeStateForFormElement):
* html/FormController.h:
(FormController):
* html/HTMLFormControlElementWithState.cpp:
(WebCore::HTMLFormControlElementWithState::finishParsingChildren):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121235 268f45cc-cd09-0410-ab3c-d52691b4dbfc