HTML Imports: Make sure new imports being added to the "first child"

Source/core/html/imports/HTMLImportsController.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 84 matching lines @@
     OwnPtr<HTMLImportChild> loader = adoptPtr(new HTMLImportChild(*m_master, url, mode));
     loader->setClient(client);
     parent->appendImport(loader.get());
     m_imports.append(loader.release());
     return m_imports.last().get();
 }
 
 HTMLImportChild* HTMLImportsController::load(HTMLImport* parent, HTMLImportChildClient* client, FetchRequest request)
 {
     ASSERT(!request.url().isEmpty() && request.url().isValid());
+    ASSERT(parent == this || toHTMLImportChild(parent)->loader()->isFirstImport(toHTMLImportChild(parent)));
 
     if (findLinkFor(request.url())) {
         HTMLImportChild* child = createChild(request.url(), parent, client);
         child->wasAlreadyLoaded();
         return child;
     }
 
     bool sameOriginRequest = securityOrigin()->canRequest(request.url());
     request.setCrossOriginAccessControl(
         securityOrigin(), sameOriginRequest ? AllowStoredCredentials : DoNotAllowStoredCredentials,
@@ skipping 108 matching lines @@
 {
     for (size_t i = 0; i < m_loaders.size(); ++i) {
         if (m_loaders[i]->document() == &document)
             return m_loaders[i].get();
     }
 
     return 0;
 }
 
 } // namespace WebCore