Upgrade: Send a 'Prefer' header for feature detection.

Source/core/fetch/ResourceFetcher.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@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
     version 2 of the License, or (at your option) any later version.
@@ skipping 182 matching lines @@
     void preCacheSubstituteDataForMainResource(const FetchRequest&, const SubstituteData&);
     void storeResourceTimingInitiatorInformation(Resource*);
     bool scheduleArchiveLoad(Resource*, const ResourceRequest&);
 
     enum RevalidationPolicy { Use, Revalidate, Reload, Load };
     RevalidationPolicy determineRevalidationPolicy(Resource::Type, const FetchRequest&, Resource* existingResource) const;
 
     void determineRequestContext(ResourceRequest&, Resource::Type);
     ResourceRequestCachePolicy resourceRequestCachePolicy(const ResourceRequest&, Resource::Type);
     void addAdditionalRequestHeaders(ResourceRequest&, Resource::Type);
-    void maybeUpgradeInsecureRequestURL(FetchRequest&);
+    void upgradeInsecureRequest(FetchRequest&);
 
     bool canRequest(Resource::Type, const ResourceRequest&, const KURL&, const ResourceLoaderOptions&, bool forPreload, FetchRequest::OriginRestriction) const;
 
     static bool resourceNeedsLoad(Resource*, const FetchRequest&, RevalidationPolicy);
 
     void notifyLoadedFromMemoryCache(Resource*);
 
     void garbageCollectDocumentResourcesTimerFired(Timer<ResourceFetcher>*);
     void scheduleDocumentResourcesGC();
 
@@ skipping 66 matching lines @@
             m_loader->m_allowStaleResources = m_previousState;
     }
 private:
     ResourceFetcher* m_loader;
     bool m_previousState;
 };
 
 } // namespace blink
 
 #endif