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

Source/core/loader/FrameFetchContext.h

 /*
  * 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 36 matching lines @@
 class ResourceResponse;
 class ResourceRequest;
 
 class FrameFetchContext final : public FetchContext {
 public:
     static PassRefPtrWillBeRawPtr<ResourceFetcher> createContextAndFetcher(DocumentLoader* loader)
     {
         return ResourceFetcher::create(adoptPtrWillBeNoop(new FrameFetchContext(loader)));
     }
 
+    static void provideDocumentToContext(FetchContext& context, Document* document)
+    {
+        ASSERT(document);
+        RELEASE_ASSERT(context.isLiveContext());
+        static_cast<FrameFetchContext&>(context).m_document = document;
+    }
+
     ~FrameFetchContext();
 
-    Document* document() const { return m_document; } // Can be null
-    void setDocument(Document* document) { m_document = document; }
-    void clearDocumentLoader() { m_documentLoader = nullptr; }
+    bool isLiveContext() { return true; }
 
     void addAdditionalRequestHeaders(ResourceRequest&, FetchResourceType) override;
     void setFirstPartyForCookies(ResourceRequest&) override;
     CachePolicy cachePolicy() const override;
     ResourceRequestCachePolicy resourceRequestCachePolicy(const ResourceRequest&, Resource::Type) const override;
     void dispatchDidChangeResourcePriority(unsigned long identifier, ResourceLoadPriority, int intraPriorityValue) override;
     void dispatchWillSendRequest(unsigned long identifier, ResourceRequest&, const ResourceResponse& redirectResponse, const FetchInitiatorInfo& = FetchInitiatorInfo()) override;
     void dispatchDidLoadResourceFromMemoryCache(const ResourceRequest&, const ResourceResponse&) override;
     void dispatchDidReceiveResponse(unsigned long identifier, const ResourceResponse&, ResourceLoader* = 0) override;
     void dispatchDidReceiveData(unsigned long identifier, const char* data, int dataLength, int encodedDataLength) override;
@@ skipping 40 matching lines @@
     // FIXME: Oilpan: Ideally this should just be a traced Member but that will
     // currently leak because ComputedStyle and its data are not on the heap.
     // See crbug.com/383860 for details.
     RawPtrWillBeWeakMember<Document> m_document;
     DocumentLoader* m_documentLoader;
 };
 
 }
 
 #endif