Use toDocument instead of static_cast<Document*>.

Source/WebKit/chromium/src/WebWorkerClientImpl.cpp

 /*
  * Copyright (C) 2009 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 54 matching lines @@
 using namespace WebCore;
 
 namespace WebKit {
 
 // Chromium-specific decorator of WorkerMessagingProxy.
 
 // static
 WorkerGlobalScopeProxy* WebWorkerClientImpl::createWorkerGlobalScopeProxy(Worker* worker)
 {
     if (worker->scriptExecutionContext()->isDocument()) {
-        Document* document = static_cast<Document*>(worker->scriptExecutionContext());
+        Document* document = toDocument(worker->scriptExecutionContext());
         WebFrameImpl* webFrame = WebFrameImpl::fromFrame(document->frame());
         WebWorkerClientImpl* proxy = new WebWorkerClientImpl(worker, webFrame);
         return proxy;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 void WebWorkerClientImpl::terminateWorkerGlobalScope()
 {
@@ skipping 66 matching lines @@
     : WebCore::WorkerMessagingProxy(worker)
     , m_webFrame(webFrame)
 {
 }
 
 WebWorkerClientImpl::~WebWorkerClientImpl()
 {
 }
 
 } // namespace WebKit