Enable `as` based priorities for <link rel=preload>

Source/core/fetch/Resource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
@@ skipping 53 matching lines @@
         MainResource,
         Image,
         CSSStyleSheet,
         Script,
         Font,
         Raw,
         SVGDocument,
         XSLStyleSheet,
         LinkPrefetch,
         LinkSubresource,
+        LinkPreload,
         TextTrack,
         ImportResource,
         Media // Audio or video file requested by a HTML5 media element
     };
 
     enum Status {
         Unknown, // let cache decide what to do with it
         Pending, // only partially loaded
         Cached, // regular case
         LoadError,
@@ skipping 336 matching lines @@
 const char* ResourceTypeName(Resource::Type);
 #endif
 
 #define DEFINE_RESOURCE_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName##Resource, Resource, resource, resource->type() == Resource::typeName, resource.type() == Resource::typeName); \
     inline typeName##Resource* to##typeName##Resource(const ResourcePtr<Resource>& ptr) { return to##typeName##Resource(ptr.get()); }
 
 }
 
 #endif