Mojo C++ bindings: reduce references to AssociatedGroupController.

mojo/public/cpp/bindings/lib/interface_ptr_state.h

Index: mojo/public/cpp/bindings/lib/interface_ptr_state.h
diff --git a/mojo/public/cpp/bindings/lib/interface_ptr_state.h b/mojo/public/cpp/bindings/lib/interface_ptr_state.h
index 78aa02e17635442ae394a7aa9d0109650fbbab1e..83379521c6cb103d471efcd73c9ea9ccb8d437ea 100644
--- a/mojo/public/cpp/bindings/lib/interface_ptr_state.h
+++ b/mojo/public/cpp/bindings/lib/interface_ptr_state.h
@@ -361,8 +361,10 @@ class InterfacePtrState<Interface, true> {
         // will not be used.
         0u));
     proxy_.reset(new Proxy(endpoint_client_.get()));
-    proxy_->serialization_context()->group_controller =
-        endpoint_client_->group_controller();
+    if (Interface::PassesAssociatedKinds_) {
+      proxy_->serialization_context()->group_controller =
+          endpoint_client_->group_controller();
+    }
   }
 
   void OnQueryVersion(const base::Callback<void(uint32_t)>& callback,