Check if stylesheet resource was cached before marking it as such.

third_party/WebKit/Source/core/css/CSSStyleSheetResourceTest.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/fetch/CSSStyleSheetResource.h"
 
 #include "core/css/CSSCrossfadeValue.h"
 #include "core/css/CSSImageValue.h"
 #include "core/css/CSSPrimitiveValue.h"
 #include "core/css/CSSProperty.h"
@@ skipping 100 matching lines @@
             for (size_t i = 0; i < imageResource->size() + 1; ++i)
                 memoryCache()->update(imageResource.get(), imageResource->size(), imageResource->size(), true);
         }
         ASSERT_TRUE(memoryCache()->isInSameLRUListForTest(cssResource.get(), imageResource.get()));
     }
     Heap::collectAllGarbage();
     // This operation should not lead to crash!
     memoryCache()->pruneAll();
 }
 
+TEST_F(CSSStyleSheetResourceTest, DuplicateResourceNotCached)
+{
+    const char url[] = "https://localhost/style.css";
+    KURL imageURL(KURL(), url);
+    KURL cssURL(KURL(), url);
+
+    // Emulate using <img> to do async stylesheet preloads.
+
+    RefPtrWillBeRawPtr<Resource> imageResource = ImageResource::create(ResourceRequest(imageURL), nullptr);
+    ASSERT_TRUE(imageResource);
+    memoryCache()->add(imageResource.get());
+    ASSERT_TRUE(memoryCache()->contains(imageResource.get()));
+
+    RefPtrWillBeRawPtr<CSSStyleSheetResource> cssResource = CSSStyleSheetResource::createForTest(ResourceRequest(cssURL), "utf-8");
+    cssResource->responseReceived(ResourceResponse(cssURL, "style/css", 0, nullAtom, String()), nullptr);
+    cssResource->finish();
+
+    RefPtrWillBeRawPtr<StyleSheetContents> contents = StyleSheetContents::create(CSSParserContext(HTMLStandardMode, nullptr));
+    RefPtrWillBeRawPtr<CSSStyleSheet> sheet = CSSStyleSheet::create(contents, document());
+    EXPECT_TRUE(sheet);
+
+    contents->checkLoaded();
+    cssResource->saveParsedStyleSheet(contents);
+
+    // Verify that the cache will have a mapping for |imageResource| at |url|.
+    // The underlying |contents| for the stylesheet resource must have a
+    // matching cache status.
+    ASSERT_TRUE(memoryCache()->contains(imageResource.get()));
+    ASSERT_FALSE(memoryCache()->contains(cssResource.get()));
+    ASSERT_FALSE(contents->isInMemoryCache());
+}
+
 } // namespace
 } // namespace blink