Keep track of fixed positioning in accessibility tree.

third_party/WebKit/public/web/WebAXObject.h

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 326 matching lines @@
   // Every object's bounding box is returned relative to a
   // container object (which is guaranteed to be an ancestor) and
   // optionally a transformation matrix that needs to be applied too.
   // To compute the absolute bounding box of an element, start with its
   // boundsInContainer and apply the transform. Then as long as its container is
   // not null, walk up to its container and offset by the container's offset
   // from origin, the container's scroll position if any, and apply the
   // container's transform.  Do this until you reach the root of the tree.
   BLINK_EXPORT void GetRelativeBounds(WebAXObject& offset_container,
                                       WebFloatRect& bounds_in_container,
-                                      SkMatrix44& container_transform) const;
+                                      SkMatrix44& container_transform,
+                                      bool& is_fixed_positioned) const;
 
   // Make this object visible by scrolling as many nested scrollable views as
   // needed.
   BLINK_EXPORT void ScrollToMakeVisible() const;
   // Same, but if the whole object can't be made visible, try for this subrect,
   // in local coordinates.
   BLINK_EXPORT void ScrollToMakeVisibleWithSubFocus(const WebRect&) const;
   // Scroll this object to a given point in global coordinates of the top-level
   // window.
   BLINK_EXPORT void ScrollToGlobalPoint(const WebPoint&) const;
 
 #if BLINK_IMPLEMENTATION
   BLINK_EXPORT WebAXObject(AXObject*);
   WebAXObject& operator=(AXObject*);
   operator AXObject*() const;
 #endif
 
  private:
   WebPrivatePtr<AXObject> private_;
 };
 
 }  // namespace blink
 
 #endif