[test] Resources served from MemoryCache - early exit

third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp

Index: third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
diff --git a/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp b/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
index 5105488d1075419512ef874a4c21adde757db359..1de2c730abec0cfe274340cf2efcf8bf6c92fa82 100644
--- a/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
+++ b/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
@@ -488,6 +488,8 @@ Resource* ResourceFetcher::requestResource(
   DCHECK(request.options().synchronousPolicy == RequestAsynchronously ||
          factory.type() == Resource::Raw ||
          factory.type() == Resource::XSLStyleSheet);
+  TRACE_EVENT1("blink", "ResourceFetcher::requestResource", "url",
+               urlForTraceEvent(request.url()));
 
   context().populateRequestData(request.mutableResourceRequest());
   if (request.resourceRequest().httpHeaderField("Upgrade-Insecure-Requests") !=
@@ -497,13 +499,30 @@ Resource* ResourceFetcher::requestResource(
   context().addClientHintsIfNecessary(request);
   context().addCSPHeaderIfNecessary(factory.type(), request);
 
-  TRACE_EVENT1("blink", "ResourceFetcher::requestResource", "url",
-               urlForTraceEvent(request.url()));
-
   if (!request.url().isValid())
     return nullptr;
 
   unsigned long identifier = createUniqueIdentifier();
+
+  // Potentially early return if this request matches a preload. We need to be
+  // careful to ensure that the preload request matches the various security
+  // properties of the load.
+  Resource* originalResource(nullptr);
+  originalResource =
+      memoryCache()->resourceForURL(request.url(), getCacheIdentifier());
+  if (originalResource) {
+    const RevalidationPolicy policy = determineRevalidationPolicy(
+        factory.type(), request, originalResource, false);
+    if (policy == Use) {
+      if (originalResource->isLinkPreload() && !request.isLinkPreload())
+        originalResource->setLinkPreload(false);
+      moveCachedNonBlockingResourceToBlocking(originalResource, request);
+      requestLoadStarted(identifier, originalResource, request,
+                         ResourceLoadingFromCache, false);
+      return originalResource;
+    }
+  }
+
   request.mutableResourceRequest().setPriority(computeLoadPriority(
       factory.type(), request, ResourcePriority::NotVisible));
   initializeResourceRequest(request.mutableResourceRequest(), factory.type(),
@@ -555,9 +574,16 @@ Resource* ResourceFetcher::requestResource(
     if (!resource && !isDataUrl && m_archive)
       return nullptr;
   }
+
+  // Only retrieve the Resource from MemoryCache if the url has been changed
+  // by the embedder.
   if (!resource) {
-    resource =
-        memoryCache()->resourceForURL(request.url(), getCacheIdentifier());
+    if (!originalResource || request.url() != originalResource->url()) {
+      resource =
+          memoryCache()->resourceForURL(request.url(), getCacheIdentifier());
+    } else {
+      resource = originalResource;
+    }
   }
 
   // See if we can use an existing resource from the cache. If so, we need to
@@ -808,10 +834,6 @@ ResourceFetcher::determineRevalidationPolicy(Resource::Type type,
   if (existingResource->response().wasFallbackRequiredByServiceWorker())
     return Reload;
 
-  // We already have a preload going for this URL.
-  if (fetchRequest.forPreload() && existingResource->isPreloaded())
-    return Use;
-
   // If the same URL has been loaded as a different type, we need to reload.
   if (existingResource->getType() != type) {
     // FIXME: If existingResource is a Preload and the new type is LinkPrefetch
@@ -823,6 +845,10 @@ ResourceFetcher::determineRevalidationPolicy(Resource::Type type,
     return Reload;
   }
 
+  // We already have a preload going for this URL.
+  if (fetchRequest.forPreload() && existingResource->isPreloaded())
+    return Use;
+
   // Do not load from cache if images are not enabled. There are two general
   // cases:
   //