Expose <dialog> in the accessibility tree by default.

Source/core/accessibility/AXRenderObject.cpp

 /*
 * Copyright (C) 2008 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 694 matching lines @@
     // Anything that is content editable should not be ignored.
     // However, one cannot just call node->rendererIsEditable() since that will ask if its parents
     // are also editable. Only the top level content editable region should be exposed.
     if (hasContentEditableAttributeSet())
         return false;
 
     // List items play an important role in defining the structure of lists. They should not be ignored.
     if (roleValue() == ListItemRole)
         return false;
 
+    if (roleValue() == DialogRole)
+        return false;
+
     // if this element has aria attributes on it, it should not be ignored.
     if (supportsARIAAttributes())
         return false;
 
     // <span> tags are inline tags and not meant to convey information if they have no other aria
     // information on them. If we don't ignore them, they may emit signals expected to come from
     // their parent. In addition, because included spans are GroupRole objects, and GroupRole
     // objects are often containers with meaningful information, the inclusion of a span can have
     // the side effect of causing the immediate parent accessible to be ignored. This is especially
     // problematic for platforms which have distinct roles for textual block elements.
@@ skipping 1667 matching lines @@
         if (label && label->renderer()) {
             LayoutRect labelRect = axObjectCache()->getOrCreate(label)->elementRect();
             result.unite(labelRect);
         }
     }
 
     return result;
 }
 
 } // namespace WebCore