Preload scan external css for @import

third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp

Index: third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp
diff --git a/third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp b/third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp
index 4812561fa37231a4f6b588e6dbd16ce2045de007..fe6dc31f81307621cdcfd3e3f6db80275ad47b07 100644
--- a/third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp
+++ b/third_party/WebKit/Source/core/html/parser/HTMLResourcePreloader.cpp
@@ -26,6 +26,7 @@
 #include "core/html/parser/HTMLResourcePreloader.h"
 
 #include "core/dom/Document.h"
+#include "core/fetch/CSSStyleSheetResource.h"
 #include "core/fetch/FetchInitiatorInfo.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/loader/DocumentLoader.h"
@@ -79,7 +80,12 @@ void HTMLResourcePreloader::preload(PassOwnPtr<PreloadRequest> preload, const Ne
     int duration = static_cast<int>(1000 * (monotonicallyIncreasingTime() - preload->discoveryTime()));
     DEFINE_STATIC_LOCAL(CustomCountHistogram, preloadDelayHistogram, ("WebCore.PreloadDelayMs", 0, 2000, 20));
     preloadDelayHistogram.count(duration);
-    m_document->loader()->startPreload(preload->resourceType(), request);
+    Resource* resource = m_document->loader()->startPreload(preload->resourceType(), request);
+    if (resource && preload->resourceType() == Resource::CSSStyleSheet && RuntimeEnabledFeatures::cssPreloadImportEnabled()) {
+        OwnPtr<CSSPreloaderResourceClient> client = adoptPtr(new CSSPreloaderResourceClient(this));
+        resource->addClient(client.get());
+        m_cssPreloaders.add(client.release());
+    }
 }
 
 } // namespace blink