Tidy up CompositorWorkerManager unit tests.

Source/modules/serviceworkers/ServiceWorkerGlobalScopeClient.cpp

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 
 namespace blink {
 
 const char* ServiceWorkerGlobalScopeClient::supplementName()
 {
     return "ServiceWorkerGlobalScopeClient";
 }
 
 ServiceWorkerGlobalScopeClient* ServiceWorkerGlobalScopeClient::from(ExecutionContext* context)
 {
-    return static_cast<ServiceWorkerGlobalScopeClient*>(WillBeHeapSupplement<WorkerClients>::from(toWorkerGlobalScope(context)->clients(), supplementName()));
+    WorkerClients* clients = toWorkerGlobalScope(context)->clients();
+    ASSERT(clients);
+    return static_cast<ServiceWorkerGlobalScopeClient*>(WillBeHeapSupplement<WorkerClients>::from(clients, supplementName()));
 }
 
 void provideServiceWorkerGlobalScopeClientToWorker(WorkerClients* clients, PassOwnPtrWillBeRawPtr<ServiceWorkerGlobalScopeClient> client)
 {
     clients->provideSupplement(ServiceWorkerGlobalScopeClient::supplementName(), client);
 }
 
 } // namespace blink