Add missing return statement.

Bug: None
Test: CQ
Change-Id: Ic9122141316852794b1024d578eec9e6e41a63e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2342077Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: Chris Letnick <cletnick@google.com>
Auto-Submit: Chris Letnick <cletnick@google.com>
Cr-Commit-Position: refs/heads/master@{#796705}

services/service_manager/service_instance.cc

@@ -473,6 +473,7 @@ void ServiceInstance::RegisterServiceInstance(
   if (!service_manager_->RegisterService(identity, std::move(service_remote),
                                          std::move(metadata_receiver))) {
     std::move(callback).Run(mojom::ConnectResult::ACCESS_DENIED);
+    return;
   }
 
   std::move(callback).Run(mojom::ConnectResult::SUCCEEDED);