Fire accessible event on web area object when scrolling

Source/core/accessibility/AXObjectCache.cpp

 /*
  * Copyright (C) 2008, 2009, 2010 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 1018 matching lines @@
     postPlatformNotification(focusedObject, AXFocusedUIElementChanged);
 }
 
 void AXObjectCache::handleScrolledToAnchor(const Node* anchorNode)
 {
     // The anchor node may not be accessible. Post the notification for the
     // first accessible object.
     postPlatformNotification(AXObject::firstAccessibleObjectFromNode(anchorNode), AXScrolledToAnchor);
 }
 
-void AXObjectCache::handleScrollPositionChanged(FrameView* scrollView)
+void AXObjectCache::handleScrollPositionChanged(FrameView* frameView)
 {
-    postPlatformNotification(getOrCreate(scrollView), AXScrollPositionChanged);
+    // Prefer to fire the scroll position changed event on the frame view's child web area, if possible.
+    AXObject* targetAXObject = getOrCreate(frameView);
+    if (targetAXObject && !targetAXObject->children().isEmpty())
+        targetAXObject = targetAXObject->children()[0].get();
+    postPlatformNotification(targetAXObject, AXScrollPositionChanged);
 }
 
 void AXObjectCache::handleScrollPositionChanged(RenderObject* renderObject)
 {
     postPlatformNotification(getOrCreate(renderObject), AXScrollPositionChanged);
 }
 
 void AXObjectCache::setCanvasObjectBounds(Element* element, const LayoutRect& rect)
 {
     AXObject* obj = getOrCreate(element);
     if (!obj)
         return;
 
     obj->setElementRect(rect);
 }
 
 } // namespace blink