dfn element should be exposed as AXGroup:AXDefinition
https://bugs.webkit.org/show_bug.cgi?id=108980

Patch by James Craig <james@cookiecrook.com> on 2013-04-16
Reviewed by Chris Fleizach.

Source/WebCore:

dfn element now exposed as AXGroup:AXDefinition. Updated existing tests.

* accessibility/AccessibilityRenderObject.cpp:
(WebCore::AccessibilityRenderObject::computeAccessibilityIsIgnored):
(WebCore::AccessibilityRenderObject::determineAccessibilityRole):

LayoutTests:

dfn element now exposed as AXGroup:AXDefinition

* platform/mac/accessibility/role-subrole-roledescription-expected.txt:
* platform/mac/accessibility/role-subrole-roledescription.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148539 268f45cc-cd09-0410-ab3c-d52691b4dbfc