Revert of Remove ResourceFetcher's access to a real FetchContext at frame detach time

Source/core/html/imports/LinkImport.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 110 matching lines @@
     return m_owner && !m_owner->async();
 }
 
 HTMLLinkElement* LinkImport::link()
 {
     return m_owner;
 }
 
 bool LinkImport::hasLoaded() const
 {
-    return m_owner && m_child && m_child->hasFinishedLoading() && !m_child->loader()->hasError();
+    // Should never be called after importChildWasDestroyed was called.
+    ASSERT(m_owner);
+    return m_child && m_child->hasFinishedLoading() && !m_child->loader()->hasError();
 }
 
 void LinkImport::ownerInserted()
 {
     if (m_child)
         m_child->ownerInserted();
 }
 
 DEFINE_TRACE(LinkImport)
 {
     visitor->trace(m_child);
     HTMLImportChildClient::trace(visitor);
     LinkResource::trace(visitor);
 }
 
 } // namespace blink