[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 22fc448516f9882cf5acd9b6b1d5fb8f699acb6d..7d56511d85f55a6c551593370ae00f4a32c84504 100644
--- a/extensions/renderer/api_binding.h
+++ b/extensions/renderer/api_binding.h
@@ -75,6 +75,10 @@ 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:
   // Handles a call an API method with the given |name| and matches the
   // arguments against |signature|.