Support aria-grabbed attribute.

Source/modules/accessibility/AXNodeObject.cpp

 /*
 * Copyright (C) 2012, 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:
 *
 * 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 1119 matching lines @@
     ariaLabeledByElements(elements);
 
     return accessibilityDescriptionForElements(elements);
 }
 
 AccessibilityRole AXNodeObject::ariaRoleAttribute() const
 {
     return m_ariaRole;
 }
 
+AccessibilityOptionalBool AXNodeObject::isAriaGrabbed() const
+{
+    const AtomicString& grabbed = getAttribute(aria_grabbedAttr);
+    if (equalIgnoringCase(grabbed, "true"))
+        return OptionalBoolTrue;
+    if (equalIgnoringCase(grabbed, "false"))
+        return OptionalBoolFalse;
+
+    return OptionalBoolUndefined;
+}
+
 // When building the textUnderElement for an object, determine whether or not
 // we should include the inner text of this given descendant object or skip it.
 static bool shouldUseAccessibilityObjectInnerText(AXObject* obj)
 {
     // Consider this hypothetical example:
     // <div tabindex=0>
     //   <h2>
     //     Table of contents
     //   </h2>
     //   <a href="#start">Jump to start of book</a>
@@ skipping 664 matching lines @@
     float range = maxValueForRange() - minValueForRange();
     float value = valueForRange();
 
     value += range * (percentChange / 100);
     setValue(String::number(value));
 
     axObjectCache()->postNotification(node(), AXObjectCacheImpl::AXValueChanged, true);
 }
 
 } // namespace blink