Port sky-scrollable to Dart

sky/engine/core/html/parser/HTMLDocumentParser.cpp

 /*
  * Copyright (C) 2010 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 376 matching lines @@
 }
 
 bool HTMLDocumentParser::isWaitingForScripts() const
 {
   return m_treeBuilder->hasParserBlockingScript() || m_scriptRunner ||
          !document()->haveImportsLoaded();
 }
 
 void HTMLDocumentParser::resumeAfterWaitingForImports()
 {
-    RefPtr<HTMLDocumentParser> protect(this);
-    ASSERT(!isWaitingForScripts());
+    if (isWaitingForScripts())
+        return;
     if (m_pendingChunks.isEmpty())
         return;
     ASSERT(m_haveBackgroundParser);
+    RefPtr<HTMLDocumentParser> protect(this);
     pumpPendingChunks();
 }
 
 // HTMLScriptRunner has finished executing a script.
 // Just call resumeAfterWaitingForImports since it happens to do what we need.
 void HTMLDocumentParser::scriptExecutionCompleted() {
   ASSERT(m_scriptRunner);
   m_scriptRunner.clear();
   // To avoid re-entering the parser for synchronous scripts, we use a postTask.
   base::MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&HTMLDocumentParser::resumeAfterWaitingForImports,
                             m_weakFactory.GetWeakPtr()));
 }
 }