Fix and IPC fuzzer top crasher in OnWorkerScriptLoaded.

content/browser/service_worker/service_worker_dispatcher_host.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/service_worker/service_worker_dispatcher_host.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/message_port_message_filter.h"
@@ skipping 672 matching lines @@
     int embedded_worker_id,
     int thread_id,
     int provider_id) {
   TRACE_EVENT0("ServiceWorker",
                "ServiceWorkerDispatcherHost::OnWorkerScriptLoaded");
   if (!GetContext())
     return;
 
   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();
   if (!registry->CanHandle(embedded_worker_id))
     return;
   registry->OnWorkerScriptLoaded(
       render_process_id_, thread_id, embedded_worker_id);
 }
 
 void ServiceWorkerDispatcherHost::OnWorkerScriptLoadFailed(
@@ skipping 256 matching lines @@
   ServiceWorkerHandle* handle = handles_.Lookup(handle_id);
   if (!handle) {
     BadMessageReceived();
     return;
   }
   handle->version()->StopWorker(
       base::Bind(&ServiceWorkerUtils::NoOpStatusCallback));
 }
 
 }  // namespace content