[Extension Bindings] Add JS custom hook support

extensions/renderer/api_bindings_system.h

Index: extensions/renderer/api_bindings_system.h
diff --git a/extensions/renderer/api_bindings_system.h b/extensions/renderer/api_bindings_system.h
index 57ce4e705aa812396b111d4881595f99bbdd7901..e7173c4ecbf0e69e9a657bcaabacb8a575455270 100644
--- a/extensions/renderer/api_bindings_system.h
+++ b/extensions/renderer/api_bindings_system.h
@@ -109,6 +109,8 @@ class APIBindingsSystem {
   // performance concern?
   std::map<std::string, std::unique_ptr<APIBindingHooks>> binding_hooks_;
 
+  binding::RunJSFunction call_js_;
+
   // The method to retrieve the DictionaryValue describing a given extension
   // API. Curried in for testing purposes so we can use fake APIs.
   GetAPISchemaMethod get_api_schema_;