External Stylesheets preloaded according to their media attribute

Source/WebCore/html/parser/HTMLResourcePreloader.cpp

 /*
  * Copyright (C) 2013 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
  */
 
 #include "config.h"
 #include "HTMLResourcePreloader.h"
 
 #include "CachedResourceLoader.h"
 #include "Document.h"
 
+#include "MediaList.h"
+#include "MediaQueryEvaluator.h"
+#include "RenderObject.h"
+
 namespace WebCore {
 
 bool PreloadRequest::isSafeToSendToAnotherThread() const
 {
     return m_initiator.isSafeToSendToAnotherThread()
         && m_charset.isSafeToSendToAnotherThread()
         && m_resourceURL.isSafeToSendToAnotherThread()
+        && m_mediaAttribute.isSafeToSendToAnotherThread()
         && m_baseURL.isSafeToSendToAnotherThread();
 }
 
 KURL PreloadRequest::completeURL(Document* document)
 {
     return document->completeURL(m_resourceURL, m_baseURL.isEmpty() ? document->url() : m_baseURL);
 }
 
 CachedResourceRequest PreloadRequest::resourceRequest(Document* document)
 {
     ASSERT(isMainThread());
     CachedResourceRequest request(ResourceRequest(completeURL(document)));
     request.setInitiator(m_initiator);
 
     // FIXME: It's possible CORS should work for other request types?
     if (m_resourceType == CachedResource::Script)
         request.mutableResourceRequest().setAllowCookies(m_crossOriginModeAllowsCookies);
     return request;
 }
 
 void HTMLResourcePreloader::takeAndPreload(PreloadRequestStream& r)
 {
     PreloadRequestStream requests;
     requests.swap(r);
 
     for (PreloadRequestStream::iterator it = requests.begin(); it != requests.end(); ++it)
         preload(it->release());
 }
 
+static bool mediaAttributeMatches(Frame* frame, RenderStyle* renderStyle, const String& attributeValue)
+{
+    RefPtr<MediaQuerySet> mediaQueries = MediaQuerySet::createAllowingDescriptionSyntax(attributeValue);
+    MediaQueryEvaluator mediaQueryEvaluator("screen", frame, renderStyle);
+    return mediaQueryEvaluator.eval(mediaQueries.get());
+}
+
 void HTMLResourcePreloader::preload(PassOwnPtr<PreloadRequest> preload)
 {
+    ASSERT(m_document->frame());
+    ASSERT(m_document->renderer());
+    ASSERT(m_document->renderer()->style());
+    if (!preload->media().isEmpty() && !mediaAttributeMatches(m_document->frame(), m_document->renderer()->style(), preload->media()))
+        return;
+
     CachedResourceRequest request = preload->resourceRequest(m_document);
     m_document->cachedResourceLoader()->preload(preload->resourceType(), request, preload->charset());
 }
 
+
 }