One accessibility tree per frame.

chrome/renderer/extensions/automation_internal_custom_bindings.h

Index: chrome/renderer/extensions/automation_internal_custom_bindings.h
diff --git a/chrome/renderer/extensions/automation_internal_custom_bindings.h b/chrome/renderer/extensions/automation_internal_custom_bindings.h
index d4228e748b25af052f946a2832f0cea2f474c4c8..bcca2ed96b8d3ae83532fe2d28a9029c77f96874 100644
--- a/chrome/renderer/extensions/automation_internal_custom_bindings.h
+++ b/chrome/renderer/extensions/automation_internal_custom_bindings.h
@@ -17,6 +17,7 @@ struct ExtensionMsg_AccessibilityEventParams;
 
 namespace extensions {
 
+class AutomationInternalCustomBindings;
 class AutomationMessageFilter;
 
 struct TreeCache {
@@ -25,9 +26,11 @@ struct TreeCache {
 
   int tab_id;
   int tree_id;
+  int parent_node_id_from_parent_tree;
 
   gfx::Vector2d location_offset;
   ui::AXTree tree;
+  AutomationInternalCustomBindings* owner;
 };
 
 struct TreeChangeObserver {
@@ -48,6 +51,8 @@ class AutomationInternalCustomBindings : public ObjectBackedNativeHandler,
 
   TreeCache* GetTreeCacheFromTreeID(int tree_id);
 
+  ui::AXNode* GetParent(ui::AXNode* node, TreeCache** in_out_cache);
+
   ScriptContext* context() const {
     return ObjectBackedNativeHandler::context();
   }