Exposing correct state for summary element depending on open attribute.

Source/core/accessibility/AXNodeObject.cpp

Index: Source/core/accessibility/AXNodeObject.cpp
diff --git a/Source/core/accessibility/AXNodeObject.cpp b/Source/core/accessibility/AXNodeObject.cpp
index 917f64a04c8d02f4d37d2d1937f2474c6f17f19c..34de3ce79857e97a883c449c1223680260058671 100644
--- a/Source/core/accessibility/AXNodeObject.cpp
+++ b/Source/core/accessibility/AXNodeObject.cpp
@@ -713,6 +713,11 @@ bool AXNodeObject::isEnabled() const
 
 AccessibilityExpanded AXNodeObject::isExpanded() const
 {
+    if (node() && isHTMLSummaryElement(*node())) {
+        if (node()->parentNode() && isHTMLDetailsElement(node()->parentNode()))
+            return toElement(node()->parentNode())->hasAttribute(openAttr) ? ExpandedExpanded : ExpandedCollapsed;
+    }
+
     const AtomicString& expanded = getAttribute(aria_expandedAttr);
     if (equalIgnoringCase(expanded, "true"))
         return ExpandedExpanded;