Keep track of fixed positioning in accessibility tree.

content/renderer/accessibility/blink_ax_tree_source.cc

Index: content/renderer/accessibility/blink_ax_tree_source.cc
diff --git a/content/renderer/accessibility/blink_ax_tree_source.cc b/content/renderer/accessibility/blink_ax_tree_source.cc
index 69a9e864a9d115799a300fde1c5f48441fe71510..c752a75b87bfd3be4f3a60c19ee0e491fbefc6af 100644
--- a/content/renderer/accessibility/blink_ax_tree_source.cc
+++ b/content/renderer/accessibility/blink_ax_tree_source.cc
@@ -389,13 +389,15 @@ void BlinkAXTreeSource::SerializeNode(WebAXObject src,
   WebAXObject offset_container;
   WebFloatRect bounds_in_container;
   SkMatrix44 container_transform;
+  bool is_fixed_positioned;
   src.GetRelativeBounds(offset_container, bounds_in_container,
-                        container_transform);
+                        container_transform, is_fixed_positioned);
   dst->location = bounds_in_container;
   if (!container_transform.isIdentity())
     dst->transform = base::WrapUnique(new gfx::Transform(container_transform));
   if (!offset_container.IsDetached())
     dst->offset_container_id = offset_container.AxID();
+  dst->is_fixed_positioned = is_fixed_positioned;
 
   AXContentNodeDataSparseAttributeAdapter sparse_attribute_adapter(dst);
   src.GetSparseAXAttributes(sparse_attribute_adapter);