Adds AX role for abbr tag.

third_party/WebKit/public/web/WebAXEnums.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 57 matching lines @@
     WebAXEventTextInserted,
     WebAXEventTextRemoved,
     WebAXEventValueChanged
 };
 
 // Accessibility roles.
 // These values must match blink::AccessibilityRole values.
 // Enforced in AssertMatchingEnums.cpp.
 enum WebAXRole {
     WebAXRoleUnknown = 0,
+    WebAXRoleAbbr,
     WebAXRoleAlertDialog,
     WebAXRoleAlert,
     WebAXRoleAnnotation,
     WebAXRoleApplication,
     WebAXRoleArticle,
     WebAXRoleBanner,
     WebAXRoleBlockquote,
     WebAXRoleBusyIndicator,
     WebAXRoleButton,
     WebAXRoleCanvas,
@@ skipping 207 matching lines @@
     WebAXDescriptionFromUninitialized = -1,
     WebAXDescriptionFromAttribute = 0,
     WebAXDescriptionFromContents,
     WebAXDescriptionFromPlaceholder,
     WebAXDescriptionFromRelatedElement,
 };
 
 } // namespace blink
 
 #endif