Don't assert when ServiceWorker::from is passed an empty promise

Source/modules/serviceworkers/ServiceWorker.cpp

 /*
  * Copyright (C) 2013 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 139 matching lines @@
         return existingServiceWorker;
     }
 
     return create(executionContext, adoptPtr(worker));
 }
 
 PassRefPtr<ServiceWorker> ServiceWorker::from(ScriptPromiseResolverWithContext* resolver, WebType* worker)
 {
     RefPtr<ServiceWorker> serviceWorker = ServiceWorker::from(resolver->scriptState()->executionContext(), worker);
     ScriptState::Scope scope(resolver->scriptState());
-    serviceWorker->waitOnPromise(resolver->promise());
+    if (!resolver->promise().isEmpty())

[haraken, 2014/06/17 00:51:55]

Shall we move this check into ServiceWorker::waitOnPromise so that we don't need
to add the same check for all call sites (although we currently don't have any
other call site of waitOnPromise)?

[falken, 2014/06/17 01:07:51]

Good idea, I've done this.

+        serviceWorker->waitOnPromise(resolver->promise());
     return serviceWorker;
 }
 
 void ServiceWorker::onPromiseResolved()
 {
     ASSERT(m_isPromisePending);
     m_isPromisePending = false;
     m_outerWorker->proxyReadyChanged();
 }
 
@@ skipping 17 matching lines @@
     , WebServiceWorkerProxy(this)
     , m_outerWorker(worker)
     , m_isPromisePending(false)
 {
     ScriptWrappable::init(this);
     ASSERT(m_outerWorker);
     m_outerWorker->setProxy(this);
 }
 
 } // namespace WebCore