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

Source/core/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     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
@@ skipping 70 matching lines @@
     case Resource::Raw:
     case Resource::TextTrack:
     case Resource::Media:
         return new RawResource(request, type);
     case Resource::XSLStyleSheet:
         return new XSLStyleSheetResource(request, charset);
     case Resource::LinkPrefetch:
         return new Resource(request, Resource::LinkPrefetch);
     case Resource::LinkSubresource:
         return new Resource(request, Resource::LinkSubresource);
+    case Resource::LinkPreload:
+        return new Resource(request, Resource::LinkPreload);
     case Resource::ImportResource:
         return new RawResource(request, type);
     }
 
     ASSERT_NOT_REACHED();
     return 0;
 }
 
-static ResourceLoadPriority loadPriority(Resource::Type type, const FetchRequest& request)
+ResourceLoadPriority ResourceFetcher::loadPriority(Resource::Type type, const FetchRequest& request)
 {
+    // TODO(yoav): Change it here so that priority can be changed even after it was resolved.
     if (request.priority() != ResourceLoadPriorityUnresolved)
         return request.priority();
 
     switch (type) {
     case Resource::MainResource:
         return ResourceLoadPriorityVeryHigh;
     case Resource::CSSStyleSheet:
         return ResourceLoadPriorityHigh;
     case Resource::Raw:
         return request.options().synchronousPolicy == RequestSynchronously ? ResourceLoadPriorityVeryHigh : ResourceLoadPriorityMedium;
@@ skipping 11 matching lines @@
         // speed-index by ~5% on average, ~14% at the 99th percentile.
         return ResourceLoadPriorityVeryLow;
     case Resource::Media:
         return ResourceLoadPriorityLow;
     case Resource::XSLStyleSheet:
         ASSERT(RuntimeEnabledFeatures::xsltEnabled());
         return ResourceLoadPriorityHigh;
     case Resource::SVGDocument:
         return ResourceLoadPriorityLow;
     case Resource::LinkPrefetch:
+    case Resource::LinkPreload:
         return ResourceLoadPriorityVeryLow;
     case Resource::LinkSubresource:
         return ResourceLoadPriorityLow;
     case Resource::TextTrack:
         return ResourceLoadPriorityLow;
     }
     ASSERT_NOT_REACHED();
     return ResourceLoadPriorityUnresolved;
 }
 
@@ skipping 51 matching lines @@
     case Resource::Image:
         return WebURLRequest::RequestContextImage;
     case Resource::Raw:
         return WebURLRequest::RequestContextSubresource;
     case Resource::ImportResource:
         return WebURLRequest::RequestContextImport;
     case Resource::LinkPrefetch:
         return WebURLRequest::RequestContextPrefetch;
     case Resource::LinkSubresource:
         return WebURLRequest::RequestContextSubresource;
+    case Resource::LinkPreload:
+        // TODO(yoav): We should give preload its own context:
+        // https://github.com/whatwg/fetch/commit/26e5cca8ab5bb4b68a8f238f41dd7364d8c276b3
+        return WebURLRequest::RequestContextSubresource;
     case Resource::TextTrack:
         return WebURLRequest::RequestContextTrack;
     case Resource::SVGDocument:
         return WebURLRequest::RequestContextImage;
     case Resource::Media: // TODO: Split this.
         return WebURLRequest::RequestContextVideo;
     }
     ASSERT_NOT_REACHED();
     return WebURLRequest::RequestContextSubresource;
 }
@@ skipping 1089 matching lines @@
     ResourceLoaderHost::trace(visitor);
 }
 
 ResourceFetcher* ResourceFetcher::toResourceFetcher(ResourceLoaderHost* host)
 {
     ASSERT(host->objectType() == ResourceLoaderHost::ResourceFetcherType);
     return static_cast<ResourceFetcher*>(host);
 }
 
 }