Prefetch @import files from CSS files.

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index cc6338bf996c3343aacd4b9733d72828ccea0f32..b872da21e18b5d2e5bea8e7705762220a4963527 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -73,13 +73,13 @@
 
 namespace WebCore {
 
-static Resource* createResource(Resource::Type type, const ResourceRequest& request, const String& charset)
+static Resource* createResource(Resource::Type type, const ResourceRequest& request, const String& charset, Document* document)
 {
     switch (type) {
     case Resource::Image:
         return new ImageResource(request);
     case Resource::CSSStyleSheet:
-        return new CSSStyleSheetResource(request, charset);
+        return new CSSStyleSheetResource(request, charset, document);
     case Resource::Script:
         return new ScriptResource(request, charset);
     case Resource::SVGDocument:
@@ -156,7 +156,7 @@ static Resource* resourceFromDataURIRequest(const ResourceRequest& request, cons
         return 0;
     ResourceResponse response(url, mimetype, data->size(), charset, String());
 
-    Resource* resource = createResource(Resource::Image, request, charset);
+    Resource* resource = createResource(Resource::Image, request, charset, 0);
     resource->setOptions(resourceOptions);
     resource->responseReceived(response);
     if (data->size())
@@ -383,7 +383,7 @@ void ResourceFetcher::preCacheSubstituteDataForMainResource(const FetchRequest&
         memoryCache()->remove(oldResource);
 
     ResourceResponse response(url, substituteData.mimeType(), substituteData.content()->size(), substituteData.textEncoding(), emptyString());
-    ResourcePtr<Resource> resource = createResource(Resource::MainResource, request.resourceRequest(), substituteData.textEncoding());
+    ResourcePtr<Resource> resource = createResource(Resource::MainResource, request.resourceRequest(), substituteData.textEncoding(), document());
     resource->setNeedsSynchronousCacheHit(substituteData.forceSynchronousLoad());
     resource->setOptions(request.options());
     resource->setDataBufferingPolicy(BufferData);
@@ -796,7 +796,7 @@ ResourcePtr<Resource> ResourceFetcher::revalidateResource(const FetchRequest& re
             revalidatingRequest.setHTTPHeaderField("If-None-Match", eTag);
     }
 
-    ResourcePtr<Resource> newResource = createResource(resource->type(), revalidatingRequest, resource->encoding());
+    ResourcePtr<Resource> newResource = createResource(resource->type(), revalidatingRequest, resource->encoding(), document());
 
     WTF_LOG(ResourceLoading, "Resource %p created to revalidate %p", newResource.get(), resource);
     newResource->setResourceToRevalidate(resource);
@@ -815,7 +815,7 @@ ResourcePtr<Resource> ResourceFetcher::loadResource(Resource::Type type, FetchRe
     WTF_LOG(ResourceLoading, "Loading Resource for '%s'.", request.resourceRequest().url().elidedString().latin1().data());
 
     addAdditionalRequestHeaders(request.mutableResourceRequest(), type);
-    ResourcePtr<Resource> resource = createResource(type, request.mutableResourceRequest(), charset);
+    ResourcePtr<Resource> resource = createResource(type, request.mutableResourceRequest(), charset, document());
 
     memoryCache()->add(resource.get());
     storeResourceTimingInitiatorInformation(resource, request);