Add AX role for blockquote tag

Source/core/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 40 matching lines @@
 
 typedef unsigned AXID;
 
 enum AccessibilityRole {
     AlertDialogRole = 1,
     AlertRole,
     AnnotationRole,
     ApplicationRole,
     ArticleRole,
     BannerRole,
+    BlockquoteRole,
     BrowserRole,
     BusyIndicatorRole,
     ButtonRole,
     CanvasRole,
     CellRole,
     CheckBoxMenuItemRole,
     CheckBoxRole,
     ColorWellRole,
     ColumnHeaderRole,
     ColumnRole,
@@ skipping 508 matching lines @@
 
     bool m_detached;
 };
 
 #define DEFINE_AX_OBJECT_TYPE_CASTS(thisType, predicate) \
     DEFINE_TYPE_CASTS(thisType, AXObject, object, object->predicate, object.predicate)
 
 } // namespace blink
 
 #endif // AXObject_h