Remove two unused AX functions for getting a FrameView*.
<https://webkit.org/b/122724>

Reviewed by Anders Carlsson.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157369 268f45cc-cd09-0410-ab3c-d52691b4dbfc
CTTE: RenderSlider always has an HTMLInputElement.
<https://webkit.org/b/122728>

Reviewed by Anders Carlsson.

This renderer is never anonymous and always has a corresponding
HTMLInputElement. Tighten this up by having the constructor take
the element by reference, and override element() with a stronger
return type.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157370 268f45cc-cd09-0410-ab3c-d52691b4dbfc