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

Source/core/html/imports/HTMLImportLoader.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 44 matching lines @@
 {
 #if !ENABLE(OILPAN)
     dispose();
 #endif
 }
 
 void HTMLImportLoader::dispose()
 {
     m_controller = nullptr;
     if (m_document) {
+        if (m_document->parser())
+            m_document->parser()->removeClient(this);
         m_document->setImportsController(nullptr);
         m_document->cancelParsing();
         m_document.clear();
     }
 }
 
 void HTMLImportLoader::startLoading(const ResourcePtr<RawResource>& resource)
 {
     setResource(resource);
 }
@@ skipping 147 matching lines @@
 #if ENABLE(OILPAN)
     visitor->trace(m_imports);
 #endif
     visitor->trace(m_document);
     visitor->trace(m_writer);
     visitor->trace(m_microtaskQueue);
     DocumentParserClient::trace(visitor);
 }
 
 } // namespace blink