Fix and IPC fuzzer top crasher in OnWorkerScriptLoaded.

content/browser/service_worker/service_worker_dispatcher_host.cc

Index: content/browser/service_worker/service_worker_dispatcher_host.cc
diff --git a/content/browser/service_worker/service_worker_dispatcher_host.cc b/content/browser/service_worker/service_worker_dispatcher_host.cc
index a210b51d89a7f319f3a21285903b2541bd72edda..89d45807fd71b712f24ccd795934aaa75970dbb7 100644
--- a/content/browser/service_worker/service_worker_dispatcher_host.cc
+++ b/content/browser/service_worker/service_worker_dispatcher_host.cc
@@ -690,7 +690,11 @@ void ServiceWorkerDispatcherHost::OnWorkerScriptLoaded(
 
   ServiceWorkerProviderHost* provider_host =
       GetContext()->GetProviderHost(render_process_id_, provider_id);
-  DCHECK(provider_host);
+  if (!provider_host) {
+    BadMessageReceived();
+    return;
+  }
+
   provider_host->SetReadyToSendMessagesToWorker(thread_id);
 
   EmbeddedWorkerRegistry* registry = GetContext()->embedded_worker_registry();