Keep track of fixed positioning in accessibility tree.

third_party/WebKit/Source/modules/accessibility/AXObject.h

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * 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.
@@ skipping 665 matching lines @@
   bool ContainerLiveRegionBusy() const;
 
   // 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.
+  // If |out_is_fixed_positioned| is set, the scroll position of the container
+  // should be ignored.
   virtual void GetRelativeBounds(AXObject** out_container,
                                  FloatRect& out_bounds_in_container,
-                                 SkMatrix44& out_container_transform) const;
+                                 SkMatrix44& out_container_transform,
+                                 bool& out_is_fixed_positioned) const;
 
   // Get the bounds in frame-relative coordinates as a LayoutRect.
   LayoutRect GetBoundsInFrameCoordinates() const;
 
   // Explicitly set an object's bounding rect and offset container.
   void SetElementRect(LayoutRect r, AXObject* container) {
     explicit_element_rect_ = r;
     explicit_container_id_ = container->AxObjectID();
   }
 
@@ skipping 147 matching lines @@
 
   bool CanReceiveAccessibilityFocus() const;
   bool NameFromContents(bool recursive) const;
 
   AccessibilityRole ButtonRoleType() const;
 
   virtual LayoutObject* LayoutObjectForRelativeBounds() const {
     return nullptr;
   }
 
+  // A simpler variant of GetRelativeBounds that can be overridden by
+  // subclasses that don't need to handle transformations or fixed
+  // positionining. Returns true if overridden by this subclass.
+  virtual bool GetSimpleRelativeBounds(
+      AXObject** out_container,
+      FloatRect& out_bounds_in_container) const {
+    return false;
+  }
+
   const AXObject* InertRoot() const;
 
   mutable Member<AXObject> parent_;
 
   // The following cached attribute values (the ones starting with m_cached*)
   // are only valid if m_lastModificationCount matches
   // AXObjectCacheImpl::modificationCount().
   mutable int last_modification_count_;
   mutable RGBA32 cached_background_color_;
   mutable bool cached_is_ignored_ : 1;
@@ skipping 21 matching lines @@
   static unsigned number_of_live_ax_objects_;
 };
 
 #define DEFINE_AX_OBJECT_TYPE_CASTS(thisType, predicate)           \
   DEFINE_TYPE_CASTS(thisType, AXObject, object, object->predicate, \
                     object.predicate)
 
 }  // namespace blink
 
 #endif  // AXObject_h