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 dff65e3e298a299c93a3726db1ac60920224bcfb..3dcea668a0752766d238bd8220f76ba26c7e2dd6 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"
@@ -49,6 +50,13 @@ DEFINE_TRACE(HTMLResourcePreloader)
     visitor->trace(m_document);
 }
 
+int HTMLResourcePreloader::countPreloads()
+{
+    if (m_document->loader())
+        return m_document->loader()->fetcher()->countPreloads();
+    return 0;
+}
+
 static void preconnectHost(PreloadRequest* request, const NetworkHintsInterface& networkHintsInterface)
 {
     ASSERT(request);
@@ -79,7 +87,15 @@ 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);
+    // Note that if the cssExternalScanner{Preload,NoPreload} settings flags are
+    // not set, this resource client does nothing.
+    if (resource && preload->resourceType() == Resource::CSSStyleSheet) {
+        OwnPtr<CSSPreloaderResourceClient> client = adoptPtr(new CSSPreloaderResourceClient(resource, this));
+        resource->addClient(client.get(), true /* passive */);
+        m_cssPreloaders.add(std::move(client));
+    }
 }
 
 } // namespace blink