Add initial link preload support

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 315 matching lines @@
 }
 
 ResourcePtr<Resource> ResourceFetcher::fetchLinkResource(Resource::Type type, FetchRequest& request)
 {
     ASSERT(type == Resource::LinkPrefetch || type == Resource::LinkSubresource);
     ASSERT(request.resourceRequest().frameType() == WebURLRequest::FrameTypeNone);
     request.mutableResourceRequest().setRequestContext(type == Resource::LinkPrefetch ? WebURLRequest::RequestContextPrefetch : WebURLRequest::RequestContextSubresource);
     return requestResource(type, request);
 }
 
+ResourcePtr<Resource> ResourceFetcher::fetchLinkPreloadResource(Resource::Type type, FetchRequest& request)
+{
+    ASSERT(request.resourceRequest().frameType() == WebURLRequest::FrameTypeNone);

[Mike West, 2015/04/07 06:26:28]

Should this have a matching `preload` context as well?

[Yoav Weiss, 2015/04/07 07:26:14]

Quite possible. Do you think it should be part of the current CL, or can that be
added later on, after I decouple context from priority?

[Mike West, 2015/04/07 12:23:01]

If you already know that you need the context, then adding it in this CL should
be pretty straightforward. If the context is debatable (there's a GitHub issue,
right?), then adding it later is fine. In that case, I'd suggest adding a TODO
here.

+    determineRequestContext(request.mutableResourceRequest(), type);
+    return requestResource(type, request);
+}
+
 ResourcePtr<RawResource> ResourceFetcher::fetchRawResource(FetchRequest& request)
 {
     ASSERT(request.resourceRequest().frameType() == WebURLRequest::FrameTypeNone);
     ASSERT(request.resourceRequest().requestContext() != WebURLRequest::RequestContextUnspecified);
     return toRawResource(requestResource(Resource::Raw, request));
 }
 
 ResourcePtr<RawResource> ResourceFetcher::fetchMainResource(FetchRequest& request, const SubstituteData& substituteData)
 {
     ASSERT(request.resourceRequest().frameType() != WebURLRequest::FrameTypeNone);
@@ skipping 944 matching lines @@
     ResourceLoaderHost::trace(visitor);
 }
 
 ResourceFetcher* ResourceFetcher::toResourceFetcher(ResourceLoaderHost* host)
 {
     ASSERT(host->objectType() == ResourceLoaderHost::ResourceFetcherType);
     return static_cast<ResourceFetcher*>(host);
 }
 
 }