ARIA role 'form' is not supported.

Source/core/accessibility/AXObject.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 58 matching lines @@
         { "contentinfo", ContentInfoRole },
         { "dialog", DialogRole },
         { "directory", DirectoryRole },
         { "grid", GridRole },
         { "gridcell", CellRole },
         { "columnheader", ColumnHeaderRole },
         { "combobox", ComboBoxRole },
         { "definition", DefinitionRole },
         { "document", DocumentRole },
         { "rowheader", RowHeaderRole },
+        { "form", FormRole },
         { "group", GroupRole },
         { "heading", HeadingRole },
         { "img", ImageRole },
         { "link", LinkRole },
         { "list", ListRole },
         { "listitem", ListItemRole },
         { "listbox", ListBoxRole },
         { "log", LogRole },
         // "option" isn't here because it may map to different roles depending on the parent element's role
         { "main", MainRole },
@@ skipping 93 matching lines @@
 
 bool AXObject::isLandmarkRelated() const
 {
     switch (roleValue()) {
     case ApplicationRole:
     case ArticleRole:
     case BannerRole:
     case ComplementaryRole:
     case ContentInfoRole:
     case FooterRole:
+    case FormRole:
     case MainRole:
     case NavigationRole:
     case RegionRole:
     case SearchRole:
         return true;
     default:
         return false;
     }
 }
 
@@ skipping 765 matching lines @@
         return ToggleButtonRole;
     if (ariaHasPopup())
         return PopUpButtonRole;
     // We don't contemplate RadioButtonRole, as it depends on the input
     // type.
 
     return ButtonRole;
 }
 
 } // namespace blink