NOT FOR REVIEW. ax tree focus with debugging

ui/accessibility/ax_tree_data.h

Index: ui/accessibility/ax_tree_data.h
diff --git a/ui/accessibility/ax_tree_data.h b/ui/accessibility/ax_tree_data.h
index 2922a18369a60c921c2c9e8b1a35c2dbfa931a0a..25e0db3d6756360a315cd6cc653d55caab1aa36f 100644
--- a/ui/accessibility/ax_tree_data.h
+++ b/ui/accessibility/ax_tree_data.h
@@ -45,6 +45,10 @@ struct AX_EXPORT AXTreeData {
   bool loaded;
   float loading_progress;
 
+  // The node with keyboard focus within this tree, if any, or -1 if no node
+  // in this tree has focus.
+  int32_t focus_id;
+
   // The current text selection within this tree, if any, expressed as the
   // node ID and character offset of the anchor (selection start) and focus
   // (selection end).