Don't attempt to revalidate a Resource with a 304 response.

third_party/WebKit/Source/core/fetch/ResourceFetcherTest.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 643 matching lines @@
     Platform::current()->getURLLoaderMockFactory()->unregisterURL(url);
     EXPECT_TRUE(memoryCache()->contains(resource));
     EXPECT_TRUE(resource->isPreloaded());
 
     // DCL reached on second fetcher
     fetcher2->clearPreloads(ResourceFetcher::ClearSpeculativeMarkupPreloads);
     EXPECT_TRUE(memoryCache()->contains(resource));
     EXPECT_FALSE(resource->isPreloaded());
 }
 
+TEST_F(ResourceFetcherTest, Revalidate304)
+{
+    KURL url(ParsedURLString, "http://127.0.0.1:8000/foo.html");
+    Resource* resource = Resource::create(url, Resource::Raw);
+    memoryCache()->add(resource);
+    ResourceResponse response;
+    response.setURL(url);
+    response.setHTTPStatusCode(304);
+    response.setHTTPHeaderField("etag", "1234567890");
+    resource->responseReceived(response, nullptr);
+    resource->finish();
+
+    ResourceFetcher* fetcher = ResourceFetcher::create(ResourceFetcherTestMockFetchContext::create());
+    FetchRequest fetchRequest = FetchRequest(url, FetchInitiatorInfo());
+    Platform::current()->getURLLoaderMockFactory()->registerURL(url, WebURLResponse(), "");
+    Resource* newResource = fetcher->requestResource(fetchRequest, TestResourceFactory(Resource::Raw));
+    fetcher->stopFetching();
+    Platform::current()->getURLLoaderMockFactory()->unregisterURL(url);
+
+    EXPECT_NE(resource, newResource);
+}
+
 } // namespace blink