Introduce new API orientation() to expose aria-orientation correctly.

Source/modules/accessibility/AXObject.h

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * 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.
@@ skipping 214 matching lines @@
     { }
 
     AccessibilityText(const String& t, const AccessibilityTextSource& s, const RefPtr<AXObject> element)
     : text(t)
     , textSource(s)
     , textElement(element)
     { }
 };
 
 enum AccessibilityOrientation {
+    AccessibilityOrientationUndefined = 0,
     AccessibilityOrientationVertical,
     AccessibilityOrientationHorizontal,
 };
 
 enum AXObjectInclusion {
     IncludeObject,
     IgnoreObject,
     DefaultBehavior,
 };
 
@@ skipping 375 matching lines @@
     // functions called here may only search up the tree (ancestors), not down.
     void updateCachedAttributeValuesIfNeeded() const;
 };
 
 #define DEFINE_AX_OBJECT_TYPE_CASTS(thisType, predicate) \
     DEFINE_TYPE_CASTS(thisType, AXObject, object, object->predicate, object.predicate)
 
 } // namespace blink
 
 #endif // AXObject_h