Revert of Revalidate using the same Resource, attempt #2

Source/core/fetch/Resource.h

Index: Source/core/fetch/Resource.h
diff --git a/Source/core/fetch/Resource.h b/Source/core/fetch/Resource.h
index 5e742ff4f84f1508b2c7924127f11a423346f1b1..8344ca9539bf61dbe8cc340d97ec42f5548f86c0 100644
--- a/Source/core/fetch/Resource.h
+++ b/Source/core/fetch/Resource.h
@@ -121,8 +121,6 @@
     const ResourceRequest& resourceRequest() const { return m_resourceRequest; }
     const ResourceRequest& lastResourceRequest() const;
 
-    void setRevalidatingRequest(const ResourceRequest& request) { m_revalidatingRequest = request; }
-
     const KURL& url() const { return m_resourceRequest.url();}
     Type type() const { return static_cast<Type>(m_type); }
     const ResourceLoaderOptions& options() const { return m_options; }
@@ -232,7 +230,9 @@
     bool canReuseRedirectChain();
     bool mustRevalidateDueToCacheHeaders();
     bool canUseCacheValidator();
-    bool isCacheValidator() const { return !m_revalidatingRequest.isNull(); }
+    bool isCacheValidator() const { return m_resourceToRevalidate; }
+    Resource* resourceToRevalidate() const { return m_resourceToRevalidate; }
+    void setResourceToRevalidate(Resource*);
     bool hasCacheControlNoStoreHeader();
 
     double currentAge() const;
@@ -267,8 +267,6 @@
 protected:
     virtual void checkNotify();
     virtual void finishOnePart();
-
-    virtual void destroyDecodedDataForFailedRevalidation() { }
 
     // Normal resource pointers will silently switch what Resource* they reference when we
     // successfully revalidated the resource. We need a way to guarantee that the Resource
@@ -300,6 +298,9 @@
     void setDecodedSize(size_t);
     void didAccessDecodedData();
 
+    void clearResourceToRevalidate();
+    void updateResponseAfterRevalidation(const ResourceResponse& validatingResponse);
+
     void finishPendingClients();
 
     HashCountedSet<ResourceClient*> m_clients;
@@ -337,7 +338,6 @@
     virtual void destroyDecodedDataIfPossible() { }
 
     ResourceRequest m_resourceRequest;
-    ResourceRequest m_revalidatingRequest;
     AtomicString m_accept;
     PersistentWillBeMember<ResourceLoader> m_loader;
     ResourceLoaderOptions m_options;
@@ -402,6 +402,18 @@
     bool m_deleted;
 #endif
 
+    // If this field is non-null we are using the resource as a proxy for checking whether an existing resource is still up to date
+    // using HTTP If-Modified-Since/If-None-Match headers. If the response is 304 all clients of this resource are moved
+    // to to be clients of m_resourceToRevalidate and the resource is deleted. If not, the field is zeroed and this
+    // resources becomes normal resource load.
+    RawPtrWillBeMember<Resource> m_resourceToRevalidate;
+
+    // If this field is non-null, the resource has a proxy for checking whether it is still up to date (see m_resourceToRevalidate).
+    RawPtrWillBeMember<Resource> m_proxyResource;
+
+    // These handles will need to be updated to point to the m_resourceToRevalidate in case we get 304 response.
+    HashSet<ResourcePtrBase*> m_handlesToRevalidate;
+
     // Ordered list of all redirects followed while fetching this resource.
     Vector<RedirectPair> m_redirectChain;
 };