Add live region root to the cached properties of an AXObject.

Source/core/accessibility/AXScrollView.cpp

 /*
  * Copyright (C) 2011 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 125 matching lines @@
 
 void AXScrollView::clearChildren()
 {
     AXObject::clearChildren();
     m_verticalScrollbar = nullptr;
     m_horizontalScrollbar = nullptr;
 }
 
 bool AXScrollView::computeAccessibilityIsIgnored() const
 {
+    // We just want to match whatever's returned by our web area, which is a child of this
+    // object. Normally cached attribute values may only search up the tree. We can't just
+    // call accessibilityIsIgnored on the web area, because the web area may search up its
+    // ancestors and call this function recursively, and we'd loop until a stack overflow.
+
+    // Instead, we first update the cached accessibilityIsIgnored value for this node to
+    // false, call accessibilityIsIgnored on the web area, then return the mathcing value.
+    m_cachedIsIgnored = false;
+    m_lastModificationCount = axObjectCache()->modificationCount();
+
     AXObject* webArea = webAreaObject();
-    if (!webArea)
-        return true;
+    if (webArea)
+        return webArea->accessibilityIsIgnored();
 
-    return webArea->accessibilityIsIgnored();
+    return true;
 }
 
 void AXScrollView::addChildren()
 {
     ASSERT(!m_haveChildren);
     m_haveChildren = true;
 
     AXObject* webArea = webAreaObject();
     if (webArea && !webArea->accessibilityIsIgnored())
         m_children.append(webArea);
@@ skipping 73 matching lines @@
     return m_scrollView;
 }
 
 void AXScrollView::scrollTo(const IntPoint& point) const
 {
     if (m_scrollView)
         m_scrollView->setScrollPosition(point);
 }
 
 } // namespace blink