[Extensions Bindings] Add a bridge to use current custom bindings

extensions/renderer/api_binding.h

Index: extensions/renderer/api_binding.h
diff --git a/extensions/renderer/api_binding.h b/extensions/renderer/api_binding.h
index 464ec86efb15e1f860f0df7287cb376c5c839630..431e732934390e7bf384cf01c519239bdf5f4d18 100644
--- a/extensions/renderer/api_binding.h
+++ b/extensions/renderer/api_binding.h
@@ -74,6 +74,10 @@ class APIBinding {
       APIEventHandler* event_handler,
       const AvailabilityCallback& is_available);
 
+  // Returns the JS interface to use when registering hooks with legacy custom
+  // bindings.
+  v8::Local<v8::Object> GetJSHookInterface(v8::Local<v8::Context> context);
+
  private:
   using APISignature = std::vector<std::unique_ptr<ArgumentSpec>>;